Internet DRAFT - draft-ietf-teas-yang-path-computation
draft-ietf-teas-yang-path-computation
TEAS Working Group I. Busi, Ed.
Internet-Draft Huawei Technologies
Intended status: Standards Track S. Belotti, Ed.
Expires: 17 August 2024 Nokia
O. Gonzalez de Dios
Telefonica
A. Sharma
Google
Y. Shi
China Unicom
14 February 2024
A YANG Data Model for requesting path computation
draft-ietf-teas-yang-path-computation-22
Abstract
There are scenarios, typically in a hierarchical Software-Defined
Networking (SDN) context, where the topology information provided by
a Traffic Engineering (TE) network provider may be insufficient for
its client to perform multi-domain path computation. In these cases
the client would need to request the TE network provider to compute
some intra-domain paths to be used by the client to choose the
optimal multi-domain paths.
This document provides a mechanism to request path computation by
augmenting the Remote Procedure Calls (RPCs) defined in RFC YYYY.
[RFC EDITOR NOTE: Please replace RFC YYYY with the RFC number of
draft-ietf-teas-yang-te once it has been published.
Moreover, this document describes some use cases where the path
computation request, via YANG-based protocols (e.g., NETCONF or
RESTCONF), can be needed.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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This Internet-Draft will expire on 17 August 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.2. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Prefixes in Data Node Names . . . . . . . . . . . . . . . 6
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Packet/Optical Integration . . . . . . . . . . . . . . . 6
2.2. Multi-domain TE networks . . . . . . . . . . . . . . . . 10
2.3. Data Center Interconnections . . . . . . . . . . . . . . 12
2.4. Backward Recursive Path Computation scenario . . . . . . 14
2.5. Hierarchical PCE scenario . . . . . . . . . . . . . . . . 15
3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1. Motivation for a YANG Model . . . . . . . . . . . . . . . 17
3.1.1. Benefits of common data models . . . . . . . . . . . 17
3.1.2. Benefits of a single interface . . . . . . . . . . . 18
3.1.3. Extensibility . . . . . . . . . . . . . . . . . . . . 18
3.2. Interactions with TE topology . . . . . . . . . . . . . . 19
3.2.1. TE topology aggregation . . . . . . . . . . . . . . . 20
3.2.2. TE topology abstraction . . . . . . . . . . . . . . . 23
3.2.3. Complementary use of the TE topology . . . . . . . . 24
3.3. Path Computation RPC . . . . . . . . . . . . . . . . . . 26
3.3.1. Temporary reporting of the computed path state . . . 28
4. Path computation and optimization for multiple paths . . . . 30
5. YANG data model for requesting Path Computation . . . . . . . 31
5.1. Synchronization of multiple path computation requests . . 32
5.2. Returned metric values . . . . . . . . . . . . . . . . . 34
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5.3. Multiple Paths Requests for the same TE tunnel . . . . . 35
5.3.1. Tunnel attributes specified by value . . . . . . . . 38
5.3.2. Tunnel attributes specified by reference . . . . . . 38
5.4. Multi-Layer Path Computation . . . . . . . . . . . . . . 41
6. YANG data model for TE path computation . . . . . . . . . . . 41
6.1. Tree diagram . . . . . . . . . . . . . . . . . . . . . . 41
6.2. YANG module . . . . . . . . . . . . . . . . . . . . . . . 53
7. Security Considerations . . . . . . . . . . . . . . . . . . . 74
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 75
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 75
9.1. Normative References . . . . . . . . . . . . . . . . . . 75
9.2. Informative References . . . . . . . . . . . . . . . . . 77
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 78
A.1. Basic Path Computation . . . . . . . . . . . . . . . . . 79
A.2. Path Computation with transient state . . . . . . . . . . 79
A.3. Path Computation with Global Path Constraint . . . . . . 80
A.4. Path Computation with Per-tunnel Path Constraint . . . . 81
A.5. Path Computation result . . . . . . . . . . . . . . . . . 82
A.6. Path Computation with Primary and Secondary Paths . . . . 83
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 93
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 94
1. Introduction
There are scenarios, typically in a hierarchical Software-Defined
Networking (SDN) context, where the topology information provided by
a Traffic Engineering (TE) network provider may be insufficient for
its client to perform multi-domain path computation. In these cases
the client would need to request the TE network provider to compute
some intra-domain paths that could be used together with its topology
information to compute the multi-domain path.
These types of scenarios can be applied to different interfaces in
different reference architectures:
* Application-Based Network Operations (ABNO) control interface
[RFC7491], in which an Application Service Coordinator can request
the ABNO controller to take in charge path calculation (see
Figure 1 in [RFC7491]).
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* Abstraction and Control of TE Networks (ACTN) [RFC8453], where a
controller hierarchy is defined. In the ACTN context, path
computation is needed on the interface between Customer Network
Controller (CNC) and Multi-Domain Service Coordinator (MDSC),
called CNC-MDSC Interface (CMI), and on the interface between MSDC
and Provisioning Network Controller (PNC), called MDSC-PNC
Interface (MPI). [RFC8454] describes an information model for the
Path Computation request.
Multiple protocol solutions can be used for communication between
different controller hierarchical levels. This document assumes
that the controllers are communicating using YANG-based protocols
(e.g., NETCONF [RFC6241] or RESTCONF [RFC8040]).
Path Computation Elements (PCEs), controllers and orchestrators
perform their operations based on Traffic Engineering Databases
(TED). Such TEDs can be described, in a technology agnostic way,
with the YANG data model for TE Topologies [RFC8795].
Furthermore, the technology specific details of the TED are
modelled in the technology specific topology models, e.g., the
[I-D.ietf-ccamp-otn-topo-yang] for Optical Transport Network (OTN)
Optical Data Unit (ODU) technologies, which augment the common TE
topology model in [RFC8795].
The availability of such topology models allows the provisioning
of the TED using YANG-based protocols (e.g., NETCONF or RESTCONF).
Furthermore, it enables a PCE/controller performing the necessary
abstractions or modifications and offering this customized
topology to another PCE/controller or high level orchestrator.
The tunnels that can be provided over the networks described with
the topology models can be also set-up, deleted and modified via
YANG- based protocols (e.g., NETCONF or RESTCONF) using the TE
tunnel YANG data model [I-D.ietf-teas-yang-te].
This document defines a YANG data model [RFC7950] that augments
the RPC defined in [I-D.ietf-teas-yang-te]. The use of this RPC
is complimentary to the configuration of a TE tunnel path in
"compute-only" mode, as described in [I-D.ietf-teas-yang-te].
The YANG data model definition does not make any assumption about
whether that the client or the server implement a "PCE"
functionality, as defined in [RFC4655], and the Path Computation
Element Communication Protocol (PCEP) protocol, as defined in
[RFC5440].
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Moreover, this document describes some use cases where a path
computation request, via YANG-based protocols (e.g., NETCONF or
RESTCONF), can be needed.
The YANG data model defined in this document conforms to the
Network Management Datastore Architecture [RFC8342].
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
TED:
The traffic engineering database is a collection of all TE
information about all TE nodes and TE links in a given network.
PCE:
A Path Computation Element (PCE) is an entity that is capable of
computing a network path or route based on a network graph, and of
applying computational constraints during the computation. The
PCE entity is an application that can be located within a network
node or component, on an out-of-network server, etc. For example,
a PCE would be able to compute the path of a TE Label Switched
Path (LSP) by operating on the TED and considering bandwidth and
other constraints applicable to the TE LSP service request.
[RFC4655].
Domain:
TE information is the data relating to nodes and TE links that is
used in the process of selecting a TE path. TE information is
usually only available within a network. We call such a zone of
visibility of TE information a domain. An example of a domain may
be an IGP area or an Autonomous System. [RFC7926]
The terminology for describing YANG data models is found in
[RFC7950].
1.2. Tree Diagram
Tree diagrams used in this document follow the notation defined in
[RFC8340].
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1.3. Prefixes in Data Node Names
In this document, names of data nodes and other data model objects
are prefixed using the standard prefix associated with the
corresponding YANG imported modules, as shown in Table 1.
+==========+==========================+===========+
| Prefix | YANG module | Reference |
+==========+==========================+===========+
| te-types | ietf-te-types | [RFCZZZZ] |
+----------+--------------------------+-----------+
| te | ietf-te | [RFCYYYY] |
+----------+--------------------------+-----------+
| te-pc | ietf-te-path-computation | RFCXXXX |
+----------+--------------------------+-----------+
Table 1: Prefixes and corresponding YANG modules
RFC Editor Note: Please replace XXXX with the RFC number assigned to
this document. Please replace YYYY with the RFC number of
[I-D.ietf-teas-yang-te] once it has been published. Please replace
ZZZZ with the RFC number of [I-D.ietf-teas-rfc8776-update] once it
has been published. Please remove this note.
2. Use Cases
This section presents some use cases, where a client needs to request
underlying SDN controllers for path computation.
The use of the YANG data model defined in this document is not
restricted to these use cases but can be used in any other use case
when deemed useful.
The presented uses cases have been grouped, depending on the
different underlying topologies: Packet/Optical Integration
(Section 2.1); multi-domain Traffic Engineered (TE) Networks
(Section 2.2); and Data Center Interconnections (Section 2.3). Use
cases in Section 2.4 and Section 2.5 respectively present how to
apply this YANG data model for standard multi-domain PCE i.e.
Backward Recursive Path Computation [RFC5441] and Hierarchical PCE
[RFC6805].
2.1. Packet/Optical Integration
In this use case, an optical domain is used to provide connectivity
to some nodes of a packet domain (see Figure 1).
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+----------------+
| |
| Packet/Optical |
| Coordinator |
| |
+---+------+-----+
| |
+------------+ |
| +-----------+
+------V-----+ |
| | +------V-----+
| Packet | | |
| Domain | | Optical |
| Controller | | Domain |
| | | Controller |
+------+-----+ +-------+----+
| |
.........V......................... |
: packet domain : |
+----+ +----+ |
| R1 |= = = = = = = = = = = = = = = =| R2 | |
+-+--+ +--+-+ |
| : : | |
| :................................ : | |
| | |
| +-----+ | |
| ...........| Opt |........... | |
| : | C | : | |
| : /+--+--+\ : | |
| : / | \ : | |
| : / | \ : | |
| +-----+ / +--+--+ \ +-----+ | |
| | Opt |/ | Opt | \| Opt | | |
+---| A | | D | | B |---+ |
+-----+\ +--+--+ /+-----+ |
: \ | / : |
: \ | / : |
: \ +--+--+ / optical<---------+
: \| Opt |/ domain :
:..........| E |..........:
+-----+
Figure 1: Packet/Optical Integration use case
Figure 1 as well as Figure 2 describe two different examples of
packet/optical topologies and only show a partial view of the packet
network connectivity, before additional packet connectivity is
provided by the optical network.
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It is assumed that the Optical Domain Controller provides to the
Packet/Optical Coordinator an abstracted view of the optical network.
A possible abstraction could be to represent the whole optical
network as one "virtual node" with "virtual ports" connected to the
access links, as shown in Figure 2.
It is also assumed that Packet Domain Controller can provide the
Packet/Optical Coordinator the information it needs to set up
connectivity between packet nodes through the optical network (e.g.,
the access links).
The path computation request helps the Packet/Optical Coordinator to
know the real connections that can be provided by the optical
network.
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.
, Packet/Optical Coordinator view ,
, +----+ , .
, | | ,
, | R2 | , .
, +----+ +------------ + /+----+ ,
, | | | |/-----/ / / , .
, | R1 |--O VP1 VP4 O / / ,
, | |\ | | /----/ / , .
, +----+ \| |/ / ,
, / O VP2 VP5 O / , .
, / | | +----+ ,
, / | | | | , .
, / O VP3 VP6 O--| R4 | ,
, +----+ /-----/|_____________| +----+ , .
, | |/ +------------ + ,
, | R3 | , .
, +----+ ,,,,,,,,,,,,,,,,,
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,.
. Packet Domain Controller view +----+ ,
only packet nodes and packet links | | , .
. with access links to the optical network | R2 | ,
, +----+ /+----+ , .
. , | | /-----/ / / ,
, | R1 |--- / / , .
. , +----+\ /----/ / ,
, / \ / / , .
. , / / ,
, / +----+ , .
. , / | | ,
, / ---| R4 | , .
. , +----+ /-----/ +----+ ,
, | |/ , .
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. , | R3 | ,
, +----+ ,,,,,,,,,,,,,,,,,.
.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,
Optical Domain Controller view , .
. only optical nodes, +--+ ,
optical links and /|OF| , .
. access links from the +--++--+ / ,
packet network |OA| \ /-----/ / , .
. , ---+--+--\ +--+/ / ,
, \ | \ \-|OE|-------/ , .
. , \ | \ /-+--+ ,
, \+--+ X | , .
. , |OB|-/ \ | ,
, +--+-\ \+--+ , .
. , / \ \--|OD|--- ,
, /-----/ +--+ +--+ , .
. , / |OC|/ ,
, +--+ , .
., ,,,,,,,,,,,,,,,,,,
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,
. Actual Physical View +----+ ,
, +--+ | | ,
. , /|OF| | R2 | ,
, +----+ +--++--+ /+----+ ,
. , | | |OA| \ /-----/ / / ,
, | R1 |---+--+--\ +--+/ / / ,
. , +----+\ | \ \-|OE|-------/ / ,
, / \ | \ /-+--+ / ,
. , / \+--+ X | / ,
, / |OB|-/ \ | +----+ ,
. , / +--+-\ \+--+ | | ,
, / / \ \--|OD|---| R4 | ,
. , +----+ /-----/ +--+ +--+ +----+ ,
, | |/ |OC|/ ,
. , | R3 | +--+ ,
, +----+ ,
.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Figure 2: Packet and Optical Topology Abstractions
In this use case, the Packet/Optical Coordinator needs to set up an
optimal underlying path for an IP link between R1 and R2.
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As depicted in Figure 2, the Packet/Optical Coordinator has only an
"abstracted view" of the physical network, and it does not know the
feasibility or the cost of the possible optical paths (e.g., VP1-VP4
and VP2-VP5), which depend on the current status of the physical
resources within the optical network and on vendor-specific optical
attributes.
The Packet/Optical Coordinator can request the underlying Optical
Domain Controller to compute a set of potential optimal paths, taking
into account optical constraints. Then, based on its own
constraints, policy and knowledge (e.g. cost of the access links), it
can choose which one of these potential paths to use to set up the
optimal end- to-end path crossing optical network.
............................
: :
O VP1 VP4 O
cost=10 /:\ /:\ cost=10
/ : \----------------------/ : \
+----+ / : cost=50 : \ +----+
| |/ : : \| |
| R1 | : : | R2 |
| |\ : : /| |
+----+ \ : /--------------------\ : / +----+
\ : / cost=55 \ : /
cost=5 \:/ \:/ cost=5
O VP2 VP5 O
: :
:..........................:
Figure 3: Packet/Optical Integration path computation example
For example, in Figure 3, the Packet/Optical Coordinator can request
the Optical Domain Controller to compute the paths between VP1-VP4
and VP2-VP5 and then decide to set up the optimal end-to-end path
using the VP2-VP5 optical path even if this is not the optimal path
from the optical domain perspective.
Considering the dynamicity of the connectivity constraints of an
optical domain, it is possible that a path computed by the Optical
Domain Controller when requested by the Packet/Optical Coordinator is
no longer valid/available when the Packet/Optical Coordinator
requests it to be set up. This is further discussed in Section 3.3.
2.2. Multi-domain TE networks
In this use case there are two TE domains which are interconnected
together by multiple inter-domains links.
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A possible example could be a multi-domain optical network.
+--------------+
| Multi-Domain |
| Controller |
+---+------+---+
| |
+------------+ |
| +-----------+
+------V-----+ |
| | |
| TE Domain | +------V-----+
| Controller | | |
| 1 | | TE Domain |
+------+-----+ | Controller |
| | 2 |
| +------+-----+
.........V.......... |
: : |
+-----+ : |
| | : .........V..........
| X | : : :
| | +-----+ +-----+ :
+-----+ | | | | :
: | C |------| E | :
+-----+ +-----+ /| | | |\ +-----+ +-----+
| | | |/ +-----+ +-----+ \| | | |
| A |----| B | : : | G |----| H |
| | | |\ : : /| | | |
+-----+ +-----+ \+-----+ +-----+/ +-----+ +-----+
: | | | | :
: | D |------| F | :
: | | | | +-----+
: +-----+ +-----+ | |
: : : | Y |
: : : | |
: TE domain 1 : : TE domain 2 +-----+
:..................: :.................:
Figure 4: Multi-domain multi-link interconnection
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In order to set up an end-to-end multi-domain TE path (e.g., between
nodes A and H), the Multi-Domain Controller needs to know the
feasibility or the cost of the possible TE paths within the two TE
domains, which depend on the current status of the physical resources
within each TE domain. This is more challenging in case of optical
networks because the optimal paths depend also on vendor-specific
optical attributes (which may be different in the two domains if they
are provided by different vendors).
In order to set up a multi-domain TE path (e.g., between nodes A and
H), the Multi-Domain Controller can request the TE Domain Controllers
to compute a set of intra-domain optimal paths and take decisions
based on the information received. For example:
* The Multi-Domain Controller asks TE Domain Controllers to provide
set of paths between A-C, A-D, E-H and F-H
* TE Domain Controllers return a set of feasible paths with the
associated costs: the path A-C is not part of this set (in optical
networks, it is typical to have some paths not being feasible due
to optical constraints that are known only by the Optical Domain
Controller)
* The Multi-Domain Controller will select the path A-D-F-H since it
is the only feasible multi-domain path and then request the TE
Domain Controllers to set up the A-D and F-H intra-domain paths
* If there are multiple feasible paths, the Multi-Domain Controller
can select the optimal path knowing the cost of the intra-domain
paths (provided by the TE domain controllers) and the cost of the
inter-domain links (known by the Multi-Domain Controller)
This approach may have some scalability issues when the number of
TE domains is quite big (e.g. 20).
In this case, it would be worthwhile using the abstract TE
topology information provided by the TE Domain Controllers to
limit the number of potential optimal end-to-end paths and then
request path computation from fewer TE Domain Controllers in order
to decide what the optimal path within this limited set is.
For more details, see Section 3.2.3.
2.3. Data Center Interconnections
In these use case, there is a TE domain which is used to provide
connectivity between Data Centers which are connected with the TE
domain using access links.
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+--------------+
| Cloud Network|
| Orchestrator |
+--------------+
| | | |
+-------------+ | | +------------------------+
| | +------------------+ |
| +--------V---+ | |
| | | | |
| | TE Network | | |
+------V-----+ | Controller | +------V-----+ |
| DC | +------------+ | DC | |
| Controller | | | Controller | |
+------------+ | +-----+ +------------+ |
| ....V...| |........ | |
| : | P | : | |
.....V..... : /+-----+\ : .....V..... |
: : +-----+ / | \ +-----+ : : |
: DC1 || : | |/ | \| | : DC2 || : |
: ||||----| PE1 | | | PE2 |---- |||| : |
: _|||||| : | |\ | /| | : _|||||| : |
: : +-----+ \ +-----+ / +-----+ : : |
:.........: : \| |/ : :.........: |
:.......| PE3 |.......: |
| | |
+-----+ +---------V--+
.....|..... | DC |
: : | Controller |
: DC3 || : +------------+
: |||| : |
: _|||||| <------------------+
: :
:.........:
Figure 5: Data Center Interconnection use case
In this use case, there is the need to transfer data from Data Center
1 (DC1) to either DC2 or DC3 (e.g. workload migration).
The optimal decision depends both on the cost of the TE path (DC1-DC2
or DC1-DC3) and of the Data Center resources within DC2 or DC3.
The Cloud Network Orchestrator needs to make a decision for optimal
connection based on TE network constraints and Data Center resources.
It may not be able to make this decision because it has only an
abstract view of the TE network (as in Section 2.1).
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The Cloud Network Orchestrator can request to the TE Network
Controller to compute the cost of the possible TE paths (e.g., DC1-
DC2 and DC1-DC3) and to the DC Controller to provide the information
it needs about the required Data Center resources within DC2 and DC3
and then it can take the decision about the optimal solution based on
this information and its policy.
2.4. Backward Recursive Path Computation scenario
[RFC5441] has defined the Virtual Source Path Tree (VSPT) flag within
the RP (Request Parameters) object in order to compute inter-domain
paths following a "Backward Recursive Path Computation" (BRPC)
method. The main principle is to forward the PCReq message up to the
destination domain. Then, each PCE involved in the computation will
compute its part of the path and send it back to the requester
through PCE Response message. The resulting computation is spread
from destination PCE to source PCE. Each PCE is in charge of merging
the path it received with the one it calculated. At the end, the
source PCE merges its local part of the path with the received one to
achieve the end-to-end path.
Figure 6 below show a typical BRPC scenario where 3 PCEs cooperate to
compute inter-domain paths.
+----------------+ +----------------+
| Domain (B) | | Domain (C) |
| | | |
| /-------|---PCEP---|--------\ |
| / | | \ |
| (PCE) | | - (PCE) |
| / <----------> |D| |
| / | Inter | - |
+---|----^-------+ Domain +----------------+
| | Link
PCEP |
| | Inter-domain Link
| |
+---|----v-------+
| | |
| | Domain (A) |
| \ |
| (PCE) - |
| |S| |
| - |
+----------------+
Figure 6: BRPC Scenario
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In this use case, a client can use the YANG data model defined in
this document to request path computation from the PCE that controls
the source of the tunnel. For example, a client can request to the
PCE of domain A to compute a path from a source S, within domain A,
to a destination D, within domain C. Then PCE of domain A will use
PCEP protocol, as per [RFC5441], to compute the path from S to D and
in turn gives the final answer to the requester.
2.5. Hierarchical PCE scenario
[RFC6805] has defined an architecture and extensions to the PCE
standard to compute inter-domain path following a hierarchical
method. Two new roles have been defined: parent PCE and child PCE.
The parent PCE is in charge to coordinate the end-to-end path
computation. For that purpose it sends to each child PCE involved in
the multi-domain path computation a PCE Request message to obtain the
local part of the path. Once received all answer through PCE
Response message, the parent PCE will merge the different local parts
of the path to achieve the end-to-end path.
Figure 7 below shows a typical hierarchical scenario where a parent
PCE request end-to-end path to the different child PCE. Note that a
PCE could take independently the role of child or parent PCE
depending of which PCE will request the path.
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-----------------------------------------------------------------
| Domain 5 |
| ----- |
| |PCE 5| |
| ----- |
| |
| ---------------- ---------------- ---------------- |
| | Domain 1 | | Domain 2 | | Domain 3 | |
| | | | | | | |
| | ----- | | ----- | | ----- | |
| | |PCE 1| | | |PCE 2| | | |PCE 3| | |
| | ----- | | ----- | | ----- | |
| | | | | | | |
| | ----| |---- ----| |---- | |
| | |BN11+---+BN21| |BN23+---+BN31| | |
| | - ----| |---- ----| |---- - | |
| | |S| | | | | |D| | |
| | - ----| |---- ----| |---- - | |
| | |BN12+---+BN22| |BN24+---+BN32| | |
| | ----| |---- ----| |---- | |
| | | | | | | |
| | ---- | | | | ---- | |
| | |BN13| | | | | |BN33| | |
| -----------+---- ---------------- ----+----------- |
| \ / |
| \ ---------------- / |
| \ | | / |
| \ |---- ----| / |
| ----+BN41| |BN42+---- |
| |---- ----| |
| | | |
| | ----- | |
| | |PCE 4| | |
| | ----- | |
| | | |
| | Domain 4 | |
| ---------------- |
| |
-----------------------------------------------------------------
Figure 7: Hierarchical domain topology from RFC6805
In this use case, a client can use the YANG data model defined in
this document to request to the parent PCE a path from a source S to
a destination D. The parent PCE will in turn contact the child PCEs
through PCEP protocol to compute the end-to-end path and then return
the computed path to the client, using the YANG data model defined in
this document. For example the YANG data model can be used to
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request to PCE5 acting as parent PCE to compute a path from source S,
within domain 1, to destination D, within domain 3. PCE5 will
contact child PCEs of domain 1, 2 and 3 to obtain local part of the
end-to-end path through the PCEP protocol. Once received the PCRep
message, it merges the answers to compute the end-to-end path and
send it back to the client.
3. Motivations
This section provides the motivation for the YANG data model defined
in this document.
Section 3.1 describes the motivation for a YANG data model to request
path computation.
Section 3.2 describes the motivation for a YANG data model which
complements the TE topology YANG data model defined in [RFC8795].
Section 3.3 describes the motivation for a YANG RPC which complements
the TE tunnel YANG data model defined in [I-D.ietf-teas-yang-te].
3.1. Motivation for a YANG Model
3.1.1. Benefits of common data models
The YANG data model for requesting path computation is closely
aligned with the YANG data models that provide (abstract) TE topology
information, i.e., [RFC8795] as well as that are used to configure
and manage TE tunnels, i.e., [I-D.ietf-teas-yang-te].
There are many benefits in aligning the data model used for path
computation requests with the YANG data models used for TE topology
information and for TE tunnels configuration and management:
* There is no need for an error-prone mapping or correlation of
information.
* It is possible to use the same endpoint identifiers in path
computation requests and in the topology modeling.
* The attributes used for path computation constraints are the same
as those used when setting up a TE tunnel.
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3.1.2. Benefits of a single interface
The system integration effort is typically lower if a single,
consistent interface is used by controllers, i.e., one data modeling
language (i.e., YANG) and a common protocol (e.g., NETCONF or
RESTCONF).
Practical benefits of using a single, consistent interface include:
1. Simple authentication and authorization: The interface between
different components has to be secured. If different protocols
have different security mechanisms, ensuring a common access
control model may result in overhead. For instance, there may be
a need to deal with different security mechanisms, e.g.,
different credentials or keys. This can result in increased
integration effort.
2. Consistency: Keeping data consistent over multiple different
interfaces or protocols is not trivial. For instance, the
sequence of actions can matter in certain use cases, or
transaction semantics could be desired. While ensuring
consistency within one protocol can already be challenging, it is
typically cumbersome to achieve that across different protocols.
3. Testing: System integration requires comprehensive testing,
including corner cases. The more different technologies are
involved, the more difficult it is to run comprehensive test
cases and ensure proper integration.
4. Middle-box friendliness: Provider and consumer of path
computation requests may be located in different networks, and
middle-boxes such as firewalls, NATs, or load balancers may be
deployed. In such environments it is simpler to deploy a single
protocol. Also, it may be easier to debug connectivity problems.
5. Tooling reuse: Implementers may want to implement path
computation requests with tools and libraries that already exist
in controllers and/or orchestrators, e.g., leveraging the rapidly
growing eco-system for YANG tooling.
3.1.3. Extensibility
Path computation is only a subset of the typical functionality of a
controller. In many use cases, issuing path computation requests
comes along with the need to access other functionality on the same
system. In addition to obtaining TE topology, for instance also
configuration of services (set-up/modification/deletion) may be
required, as well as:
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1. Receiving notifications for topology changes as well as
integration with fault management
2. Performance management such as retrieving monitoring and
telemetry data
3. Service assurance, e.g., by triggering OAM functionality
4. Other fulfilment and provisioning actions beyond tunnels and
services, such as changing QoS configurations
YANG is a very extensible and flexible data modeling language
that can be used for all these use cases.
3.2. Interactions with TE topology
The use cases described in Section 2 have been described assuming
that the topology view exported by each underlying controller to its
client is aggregated using the "virtual node model", defined in
[RFC7926].
TE topology information, e.g., as provided by [RFC8795], could in
theory be used by an underlying controller to provide TE information
to its client thus allowing a PCE available within its client to
perform multi-domain path computation on its own, without requesting
path computations to the underlying controllers.
In case the client does not implement a PCE function, as discussed in
Section 1, it could not perform path computation based on TE topology
information and would instead need to request path computation from
the underlying controllers to get the information it needs to find
the optimal end-to-end path.
In case the client implements a PCE function, as discussed in
Section 1, the TE topology information needs to be complete and
accurate, which would bring to scalability issues.
Using TE topology to provide a "virtual link model" aggregation, as
described in [RFC7926], may be insufficient, unless the aggregation
provides complete and accurate information, which would still cause
scalability issues, as described in Section 3.2.1 below.
Using TE topology abstraction, as described in [RFC7926], may lead to
compute an unfeasible path, as described in [RFC7926] in
Section 3.2.2 below.
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Therefore when computing an optimal multi-domain path, there is a
scalability trade-off between providing complete and accurate TE
information and the number of path computation requests to the
underlying controllers.
The TE topology information used, in a complimentary way, to reduce
the number for path computation requests to the underlying
controllers, are described in Section 3.2.3 below.
3.2.1. TE topology aggregation
Using the TE topology model, as defined in [RFC8795], the underlying
controller can export the whole TE domain as a single TE node with a
"detailed connectivity matrix" (which provides specific TE
attributes, such as delay, Shared Risk Link Groups (SRLGs) and other
TE metrics, between each ingress and egress links).
The information provided by the "detailed connectivity matrix" would
be equivalent to the information that should be provided by "virtual
link model" as defined in [RFC7926].
For example, in the Packet/Optical Integration use case, described in
Section 2.1, the Optical Domain Controller can make the information
shown in Figure 3 available to the Packet/Optical Coordinator as part
of the TE topology information and the Packet/Optical Coordinator
could use this information to calculate on its own the optimal path
between R1 and R2, without requesting any additional information to
the Optical Domain Controller.
However, when designing the amount of information to provide within
the "detailed connectivity matrix", there is a tradeoff to be
considered between accuracy (i.e., providing "all" the information
that might be needed by the PCE available within the client) and
scalability.
Figure 8 below shows another example, similar to Figure 3, where
there are two possible Optical paths between VP1 and VP4 with
different properties (e.g., available bandwidth and cost).
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............................
: /--------------------\ :
: / cost=65 \ :
:/ available-bw=10G \:
O VP1 VP4 O
cost=10 /:\ /:\ cost=10
/ : \----------------------/ : \
+----+ / : cost=50 : \ +----+
| |/ : available-bw=2G : \| |
| R1 | : : | R2 |
| |\ : : /| |
+----+ \ : /--------------------\ : / +----+
\ : / cost=55 \ : /
cost=5 \:/ available-bw=3G \:/ cost=5
O VP2 VP5 O
: :
:..........................:
Figure 8: Packet/Optical Integration path computation Example
with multiple choices
If the information in the "detailed connectivity matrix" is not
complete/accurate, we can have the following drawbacks:
* If only the VP1-VP4 path with available bandwidth of 2 Gb/s and
cost 50 is reported, the client's PCE will fail to compute a 5 Gb/
s path between routers R1 and R2, although this would be feasible;
* If only the VP1-VP4 path with available bandwidth of 10 Gb/s and
cost 65 is reported, the client's PCE will compute, as optimal,
the 1 Gb/s path between R1 and R2 going through the VP2-VP5 path
within the optical domain while the optimal path would actually be
the one going thought the VP1-VP4 sub-path (with cost 50) within
the optical domain.
Reporting all the information, as in Figure 8, using the "detailed
connectivity matrix", is quite challenging from a scalability
perspective. The amount of this information is not just based on
number of end points (which would scale as N-square), but also on
many other parameters, including client rate, user constraints/
policies for the service, e.g. max latency < N ms, max cost, etc.,
exclusion policies to route around busy links, min Optical Signal
to Noise Ratio (OSNR) margin, max pre-Forward Error Correction
(FEC) Bit Error Rate (BER) etc. All these constraints could be
different based on connectivity requirements.
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It is also worth noting that the "connectivity matrix" has been
originally defined in Wavelength Switched Optical Networks (WSON),
[RFC7446], to report the connectivity constrains of a physical
node within the Wavelength Division Multiplexing (WDM) network:
the information it contains is pretty "static" and therefore, once
taken and stored in the TE data base, it can be always being
considered valid and up-to-date in path computation request.
The "connectivity matrix" is sometimes confused with "optical
reach table" that contain multiple (e.g. k-shortest) regen-free
reachable paths for every A-Z node combination in the network.
Optical reach tables can be calculated offline, utilizing vendor
optical design and planning tools, and periodically uploaded to
the Controller: these optical path reach tables are fairly static.
However, to get the connectivity matrix, between any two sites,
either a regen free path can be used, if one is available, or
multiple regen free paths are concatenated to get from the source
to the destination, which can be a very large combination.
Additionally, when the optical path within optical domain needs to
be computed, it can result in different paths based on input
objective, constraints, and network conditions. In summary, even
though "optical reach table" is fairly static, which regen free
paths to build the connectivity matrix between any source and
destination is very dynamic, and is done using very sophisticated
routing algorithms.
Using the "basic connectivity matrix" with an abstract node to
abstract the information regarding the connectivity constraints of
an Optical domain, would make this information more "dynamic"
since the connectivity constraints of an optical domain can change
over time because some optical paths that are feasible at a given
time may become unfeasible at a later time when e.g., another
optical path is established.
The information in the "detailed connectivity matrix" is even more
dynamic since the establishment of another optical path may change
some of the parameters (e.g., delay or available bandwidth) in the
"detailed connectivity matrix" while not changing the feasibility
of the path.
There is therefore the need to keep the information in the
"detailed connectivity matrix" updated which means that there
another tradeoff between the accuracy (i.e., providing "all" the
information that might be needed by the client's PCE) and having
up-to-date information. The more the information is provided and
the longer it takes to keep it up-to-date which increases the
likelihood that the client's PCE computes paths using not updated
information.
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It seems therefore quite challenging to have a "detailed
connectivity matrix" that provides accurate, scalable and updated
information to allow the client's PCE to take optimal decisions by
its own.
Considering the example in Figure 8 with the approach defined in
this document, the client, when it needs to set up an end-to-end
path, it can request the Optical Domain Controller to compute a
set of optimal paths (e.g., for VP1-VP4 and VP2-VP5) and take
decisions based on the information received:
* When setting up a 5 Gb/s path between routers R1 and R2, the
Optical Domain Controller may report only the VP1-VP4 path as the
only feasible path: the Packet/Optical Coordinator can
successfully set up the end-to-end path passing though this
optical path;
* When setting up a 1 Gb/s path between routers R1 and R2, the
Optical Domain Controller (knowing that the path requires only 1
Gb/s) can report both the VP1-VP4 path, with cost 50, and the VP2-
VP5 path, with cost 65. The Packet/Optical Coordinator can then
compute the optimal path which is passing thought the VP1-VP4 sub-
path (with cost 50) within the optical domain.
3.2.2. TE topology abstraction
Using the TE topology model, as defined in [RFC8795], the underlying
controller can export to its client an abstract TE topology, composed
by a set of TE nodes and TE links, representing the abstract view of
the topology under its control.
For example, in the multi-domain TE network use case, described in
Section 2.2, the TE Domain Controller 1 can export a TE topology
encompassing the TE nodes A, B, C and D and the TE links
interconnecting them. In a similar way, the TE Domain Controller 2
can export a TE topology encompassing the TE nodes E, F, G and H and
the TE links interconnecting them.
In this example, for simplicity reasons, each abstract TE node maps
with each physical node, but this is not necessary.
In order to set up a multi-domain TE path (e.g., between nodes A and
H), the Multi-Domain Controller can compute by its own an optimal
end-to-end path based on the abstract TE topology information
provided by the domain controllers. For example:
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* Multi-Domain Controller can compute, based on its own TED data,
the optimal multi-domain path being A-B-C-E-G-H, and then request
the TE Domain Controllers to set up the A-B-C and E-G-H intra-
domain paths
* But, during path set-up, the TE Domain Controller may find out
that A-B-C intra-domain path is not feasible (as discussed in
Section 2.2, in optical networks it is typical to have some paths
not being feasible due to optical constraints that are known only
by the Optical Domain Controller), while only the path A-B-D is
feasible
* So what the Multi-Domain Controller has computed is not good and
it needs to re-start the path computation from scratch
As discussed in Section 3.2.1, providing more extensive abstract
information from the TE Domain Controllers to the Multi-Domain
Controller may lead to scalability problems.
In a sense this is similar to the problem of routing and
wavelength assignment within an optical domain. It is possible to
do first routing (step 1) and then wavelength assignment (step 2),
but the chances of ending up with a good path is low.
Alternatively, it is possible to do combined routing and
wavelength assignment, which is known to be a more optimal and
effective way for optical path set-up. Similarly, it is possible
to first compute an abstract end-to-end path within the Multi-
Domain Controller (step 1) and then compute an intra-domain path
within each optical domain (step 2), but there are more chances
not to find a path or to get a suboptimal path than by performing
multiple per-domain path computations and then stitching them
together.
3.2.3. Complementary use of the TE topology
As discussed in Section 2.2, there are some scalability issues with
path computation requests in a multi-domain TE network with many TE
domains, in terms of the number of requests to send to the TE Domain
Controllers. It would therefore be worthwhile using the abstract TE
topology information provided by the TE Domain Controllers to limit
the number of requests.
An example can be described considering the multi-domain abstract TE
topology shown in Figure 9. In this example, an end-to-end TE path
between domains A and F needs to be set up. The transit TE domain
should be selected between domains B, C, D and E.
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.........B.........
: _ _ _ _ _ _ _ _ :
:/ \:
+---O NOT FEASIBLE O---+
cost=5| : : |
......A...... | :.................: | ......F......
: : | | : :
: O-----+ .........C......... +-----O :
: : : /-------------\ : : :
: : :/ \: : :
: cost<=20 O---------O cost <= 30 O---------O cost<=20 :
: /: cost=5 : : cost=5 :\ :
: /------/ : :.................: : \------\ :
: / : : \ :
:/ cost<=25 : .........D......... : cost<=25 \:
O-----------O-------+ : /-------------\ : +-------O-----------O
:\ : cost=5| :/ \: |cost=5 : /:
: \ : +-O cost <= 30 O-+ : / :
: \------\ : : : : /------/ :
: cost>=30 \: :.................: :/ cost>=30 :
: O-----+ +-----O :
:...........: | .........E......... | :...........:
| : /-------------\ : |
cost=5| :/ \: |cost=5
+---O cost >= 30 O---+
: :
:.................:
Figure 9: Multi-domain with many domains (Topology information)
The actual cost of each intra-domain path is not known a priori from
the abstract topology information. The Multi-Domain Controller only
knows, from the TE topology provided by the underlying domain
controllers, the feasibility of some intra-domain paths and some
upper-bound and/or lower-bound cost information. With this
information, together with the cost of inter-domain links, the Multi-
Domain Controller can understand by its own that:
* Domain B cannot be selected as the path connecting domains A and F
is not feasible;
* Domain E cannot be selected as a transit domain since it is known
from the abstract topology information provided by domain
controllers that the cost of the multi-domain path A-E-F (which is
100, in the best case) will be always be higher than the cost of
the multi-domain paths A-D-F (which is 90, in the worst case) and
A-C-F (which is 80, in the worst case).
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Therefore, the Multi-Domain Controller can understand by its own
that the optimal multi-domain path could be either A-D-F or A-C-F
but it cannot know which one of the two possible option actually
provides the optimal end-to-end path.
The Multi-Domain Controller can therefore request path computation
only to the TE Domain Controllers A, D, C and F (and not to all
the possible TE Domain Controllers).
.........B.........
: :
+---O O---+
......A...... | :.................: | ......F......
: : | | : :
: O-----+ .........C......... +-----O :
: : : /-------------\ : : :
: : :/ \: : :
: cost=15 O---------O cost = 25 O---------O cost=10 :
: /: cost=5 : : cost=5 :\ :
: /------/ : :.................: : \------\ :
: / : : \ :
:/ cost=10 : .........D......... : cost=15 \:
O-----------O-------+ : /-------------\ : +-------O-----------O
: : cost=5| :/ \: |cost=5 : :
: : +-O cost = 15 O-+ : :
: : : : : :
: : :.................: : :
: O-----+ +-----O :
:...........: | .........E......... | :...........:
| : : |
+---O O---+
:.................:
Figure 10: Multi-domain with many domains (Path Computation
information)
Based on these requests, the Multi-Domain Controller can know the
actual cost of each intra-domain paths which belongs to potential
optimal end-to-end paths, as shown in Figure 10, and then compute the
optimal end-to-end path (e.g., A-D-F, having total cost of 50,
instead of A-C-F having a total cost of 70).
3.3. Path Computation RPC
The TE tunnel YANG data model, defined in [I-D.ietf-teas-yang-te],
can support the need to request path computation, as described in
section 5.1.2 of [I-D.ietf-teas-yang-te].
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This solution is stateful since the state of each created "compute-
only" TE tunnel path needs to be maintained, in the YANG datastores
(at least in the running datastore and operational datastore), and
updated, when underlying network conditions change.
The RPC mechanism allows requesting path computation using a simple
atomic operation, without creating any state in the YANG datastores,
and it is the natural option/choice, especially with stateless PCE.
It is very useful to provide both the options of using an RPC as well
as of setting up TE tunnel paths in "compute-only" mode. It is
suggested to use the RPC as much as possible and to rely on "compute-
only" TE tunnel paths, when really needed.
Using the RPC solution would imply that the underlying controller
(e.g., a PNC) computes a path twice during the process to set up an
LSP: at time T1, when its client (e.g., an MDSC) sends a path
computation RPC request to it, and later, at time T2, when the same
client (MDSC) creates a TE tunnel requesting the set-up of the LSP.
The underlying assumption is that, if network conditions have not
changed, the same path that has been computed at time T1 is also
computed at time T2 by the underlying controller (e.g. PNC) and
therefore the path that is set up at time T2 is exactly the same path
that has been computed at time T1.
However, since the operation is stateless, there is no guarantee that
the returned path would still be available when path set-up is
requested: this does not cause major issues when the time between
path computation and path set-up is short (especially if compared
with the time that would be needed to update the information of a
very detailed connectivity matrix).
In most of the cases, there is even no need to guarantee that the
path that has been set up is the exactly same as the path that has
been returned by path computation, especially if it has the same or
even better metrics. Depending on the abstraction level applied by
the server, the client may also not know the actual computed path.
The most important requirement is that the required global objectives
(e.g., multi-domain path metrics and constraints) are met. For this
reason a path verification phase is always necessary to verify that
the actual path that has been set up meets the global objectives (for
example in a multi-domain network, the resulting end-to-end path
meets the required end-to-end metrics and constraints).
In most of the cases, even if the path being set up is not exactly
the same as the path returned by path computation, its metrics and
constraints are "good enough" and the path verification passes
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successfully. In the few corner cases where the path verification
fails, it is possible repeat the whole process (path computation,
path set-up and path verification).
In case it is required to set up at T2 exactly the same path computed
at T1, the RPC solution should not be used and, instead, a "compute-
only" TE tunnel path should be set up, allowing also notifications in
case the computed path has been changed.
In this case, at time T1, the client (MDSC) creates a TE tunnel in a
compute-only mode in the running datastore and later, at time T2,
changes the configuration of that TE tunnel (not to be any more in a
compute-only mode) to trigger the set-up of the LSP over the path
which have been computed at time T1 and reported in the operational
datastore.
It is worth noting that also using the "compute-only" TE tunnel path,
although increasing the likelihood that the computed path is
available at path set-up, does not guarantee that because
notifications may not be reliable or delivered on time. Path
verification is needed also in this case.
The solution based on "compute-only" TE tunnel path has also the
following drawbacks:
* Several messages required for any path computation
* Requires persistent storage in the underlying controller
* Need for garbage collection for stranded paths
* Process burden to detect changes on the computed paths in order to
provide notifications update
3.3.1. Temporary reporting of the computed path state
This section describes an optional extension to the stateless
behavior of the path computation RPC, where the underlying
controller, after having received a path computation RPC request,
maintains some "transient state" associated with the computed path,
allowing the client to request the set-up of exactly that path, if
still available.
This is similar to the "compute-only" TE tunnel path solution but, to
avoid the drawbacks of the stateful approach, is leveraging the path
computation RPC and the separation between configuration and
operational datastore, as defined in the NMDA architecture [RFC8342].
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The underlying controller, after having computed a path, as requested
by a path computation RPC, also creates a TE tunnel instance within
the operational datastore, to store that computed path. This would
be similar to a "compute-only" TE tunnel path, with the only
difference that there is no associated TE tunnel instance within the
running datastore.
Since the underlying controller stores in the operational datastore
the computed path based on an abstract topology it exposes, it also
remembers, internally, which is the actual native path (physical
path), within its native topology (physical topology), associated
with that compute-only TE tunnel instance.
Afterwards, the client (e.g., MDSC) can request the set-up of that
specific path by creating a TE tunnel instance (not in compute-only
mode) in the running datastore using the same tunnel-name of the
existing TE tunnel in the operational datastore: this will trigger
the underlying controller to set up that path, if still available.
There are still cases where the path being set up is not exactly the
same as the path that has been computed:
* When the tunnel is configured with path constraints which are not
compatible with the computed path;
* When the tunnel set-up is requested after the resources of the
computed path are no longer available;
* When the tunnel set-up is requested after the computed path is no
longer known (e.g. due to a server reboot) by the underlying
controller.
In all these cases, the underlying controller should compute and
set up a new path.
Therefore the "path verification" phase, as described in
Section 3.3 above, is always needed to check that the path that
has been set up is still "good enough".
Since this new approach is not completely stateless, garbage
collection is implemented using a timeout that, when it expires,
triggers the removal of the computed path from the operational
datastore. This operation is fully controlled by the underlying
controller without the need for any action to be taken by the
client that is not able to act on the operational datastore. The
default value of this timeout is 10 minutes but a different value
may be configured by the client.
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In addition, it is possible for the client to tag each path
computation request with a transaction-id allowing for a faster
removal of all the paths associated with a transaction-id, without
waiting for their timers to expire.
The underlying controller can remove from the operational
datastore all the paths computed with a given transaction-id which
have not been set up either when it receives a Path Delete RPC
request for that transaction-id or, automatically, right after the
set-up up of a path that has been previously computed with that
transaction-id.
This possibility is useful when multiple paths are computed but,
at most, only one is set up (e.g., in multi-domain path
computation scenario scenarios). After the selected path has been
set up (e.g, in one domain during multi-domain path set-up), all
the other alternative computed paths can be automatically deleted
by the underlying controller (since no longer needed). The client
can also request, using the Path Delete RPC request, the
underlying controller to remove all the computed paths, if none of
them is going to be set up (e.g., in a transit domain not being
selected by multi-domain path computation and so not being
automatically deleted).
This approach is complimentary and not alternative to the timer
which is always needed to avoid stranded computed paths being
stored in the operational datastore when no path is set up and no
explicit Path Delete RPC request is received.
4. Path computation and optimization for multiple paths
There are use cases, where it is advantageous to request path
computation for a set of paths, through a network or through a
network domain, using a single request [RFC5440].
In this case, sending a single request for multiple path
computations, instead of sending multiple requests for each path
computation, would reduce the protocol overhead and it would consume
less resources (e.g., threads in the client and server).
In the context of a typical multi-domain TE network, there could
multiple choices for the ingress/egress points of a domain and the
Multi-Domain Controller needs to request path computation between all
the ingress/egress pairs to select the best pair. For example, in
the example of Section 2.2, the Multi-Domain Controller needs to
request the TE Network Controller 1 to compute the A-C and the A-D
paths and to the TE Network Controller 2 to compute the E-H and the
F-H paths.
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It is also possible that the Multi-Domain Controller receives a
request to set up a group of multiple end to end connections. The
Multi-Domain Controller needs to request each TE domain Controller to
compute multiple paths, one (or more) for each end to end connection.
There are also scenarios where it can be needed to request path
computation for a set of paths in a synchronized fashion.
One example could be computing multiple diverse paths. Computing a
set of diverse paths in an unsynchronized fashion, leads to the
possibility of not being able to satisfy the diversity requirement.
In this case, it is preferable to compute a sub-optimal primary path
for which a diversely routed secondary path exists.
There are also scenarios where it is needed to request optimizing a
set of paths using objective functions that apply to the whole set of
paths, see [RFC5541], e.g. to minimize the sum of the costs of all
the computed paths in the set.
5. YANG data model for requesting Path Computation
This document define a YANG RPC to request path computation as an
"augmentation" of tunnel-rpc, defined in [I-D.ietf-teas-yang-te].
This model provides the RPC input attributes that are needed to
request path computation and the RPC output attributes that are
needed to report the computed paths.
augment /te:tunnels-path-compute/te:input/te:path-compute-info:
+-- path-request* [request-id]
| ...
augment /te:tunnels-path-compute/te:output/te:path-compute-result:
+--ro response* [response-id]
+--ro response-id uint32
+--ro computed-paths-properties
| +--ro computed-path-properties* [k-index]
| ...
This model extensively re-uses the grouping defined in
[I-D.ietf-teas-yang-te] and [I-D.ietf-teas-rfc8776-update] to ensure
maximal syntax and semantics commonality.
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This YANG data model allows one RPC to include multiple path
requests, each path request being identified by a request-id.
Therefore, one RPC can return multiple responses, one for each path
request, being identified by a response-id equal to the corresponding
request-id. Each response reports one or more computed paths, as
requested by the k-requested-paths attribute. By default, each
response reports one computed path.
5.1. Synchronization of multiple path computation requests
The YANG data model permits the synchronization of a set of multiple
path requests (identified by specific request-id) all related to a
"svec" container emulating the syntax of the Synchronization VECtor
(SVEC) PCEP object, defined in [RFC5440].
+-- synchronization* []
+-- svec
| +-- relaxable? boolean
| +-- disjointness? te-path-disjointness
| +-- request-id* uint32
+-- svec-constraints
| +-- path-metric-bound* [metric-type]
| +-- metric-type identityref
| +-- upper-bound? uint64
+-- path-srlgs-lists
| +-- path-srlgs-list* [usage]
| +-- usage identityref
| +-- values* srlg
+-- path-srlgs-names
| +-- path-srlgs-name* [usage]
| +-- usage identityref
| +-- names* string
+-- exclude-objects
| +-- excludes* []
| +-- (type)?
| +--:(numbered-node-hop)
| | +-- numbered-node-hop
| | +-- node-id te-node-id
| | +-- hop-type? te-hop-type
| +--:(numbered-link-hop)
| | +-- numbered-link-hop
| | +-- link-tp-id te-tp-id
| | +-- hop-type? te-hop-type
| | +-- direction? te-link-direction
| +--:(unnumbered-link-hop)
| | +-- unnumbered-link-hop
| | +-- link-tp-id te-tp-id
| | +-- node-id te-node-id
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| | +-- hop-type? te-hop-type
| | +-- direction? te-link-direction
| +--:(as-number)
| | +-- as-number-hop
| | +-- as-number inet:as-number
| | +-- hop-type? te-hop-type
| +--:(label)
| +-- label-hop
| +-- te-label
| ...
+-- optimizations
+-- (algorithm)?
+--:(metric) {te-types:path-optimization-metric}?
| +-- optimization-metric* [metric-type]
| +-- metric-type identityref
| +-- weight? uint8
+--:(objective-function)
{te-types:path-optimization-objective-function}?
+-- objective-function
+-- objective-function-type? identityref
The model, in addition to the metric types, defined in
[I-D.ietf-teas-rfc8776-update], which can be applied to each
individual path request, supports also additional metric types, which
apply to a set of synchronized requests, as referenced in [RFC5541].
These additional metric types are defined by the following YANG
identities:
* svec-metric-type: base YANG identity from which cumulative metric
types identities are derived.
* svec-metric-cumul-te: cumulative TE cost metric type, as defined
in [RFC5541].
* svec-metric-cumul-igp: cumulative IGP cost metric type, as defined
in [RFC5541].
* svec-metric-cumul-hop: cumulative Hop metric type, representing
the cumulative version of the Hop metric type defined in
[I-D.ietf-teas-rfc8776-update].
* svec-metric-aggregate-bandwidth-consumption: aggregate bandwidth
consumption metric type, as defined in [RFC5541].
* svec-metric-load-of-the-most-loaded-link: load of the most loaded
link metric type, as defined in [RFC5541].
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5.2. Returned metric values
This YANG data model provides a way to return the values of the
metrics computed by the path computation in the output of RPC,
together with other important information (e.g. SRLG, affinities,
explicit route), emulating the syntax of the "C" flag of the "METRIC"
PCEP object [RFC5440]:
| +--ro path-properties
| +--ro path-metric* [metric-type]
| | +--ro metric-type identityref
| | +--ro accumulative-value? uint64
| +--ro path-affinities-values
| | +--ro path-affinities-value* [usage]
| | +--ro usage identityref
| | +--ro value? admin-groups
| +--ro path-affinity-names
| | +--ro path-affinity-name* [usage]
| | +--ro usage identityref
| | +--ro affinity-name* [name]
| | +--ro name string
| +--ro path-srlgs-lists
| | +--ro path-srlgs-list* [usage]
| | +--ro usage identityref
| | +--ro values* srlg
| +--ro path-srlgs-names
| | +--ro path-srlgs-name* [usage]
| | +--ro usage identityref
| | +--ro names* string
| +--ro path-route-objects
| | ...
| +--ro te-bandwidth
| | ...
| +--ro disjointness-type?
| te-types:te-path-disjointness
It also allows the client to request which information (metrics, SRLG
and/or affinities) should be returned:
| +-- request-id uint32
| ...
| +-- requested-metrics* [metric-type]
| | +-- metric-type identityref
| +-- return-srlgs? boolean
| +-- return-affinities? boolean
| ...
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This feature is essential for path computation in a multi-domain TE
network as described in Section 2.2. In this case, the metrics
returned by a path computation requested to a given underlying
controller must be used by the client to compute the best end-to-end
path. If they are missing, the client cannot compare different paths
calculated by the underlying controllers and choose the best one for
the optimal end-to-end (e2e) path.
5.3. Multiple Paths Requests for the same TE tunnel
The YANG data model allows including multiple requests for different
paths intended to be used within the same tunnel or within different
tunnels.
When multiple requested paths are intended to be used within the same
tunnel (e.g., requesting path computation for the primary and
secondary paths of a protected tunnel), the set of attributes that
are intended to be configured on per-tunnel basis rather than on per-
path basis are common to all these path requests. These attributes
includes both attributes which can be configured only a per-tunnel
basis (e.g., tunnel-name, source/destination TTP, encoding and
switching-type) as well attributes which can be configured both on a
per-tunnel and on a per-path basis (e.g., the te-bandwidth or the
associations).
Therefore, a tunnel-attributes list is defined, within the path
computation request RPC:
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+-- tunnel-attributes* [tunnel-name]
| +-- tunnel-name string
| +-- encoding? identityref
| +-- switching-type? identityref
| +-- source? te-types:te-node-id
| +-- destination? te-types:te-node-id
| +-- src-tunnel-tp-id? binary
| +-- dst-tunnel-tp-id? binary
| +-- bidirectional? boolean
| +-- association-objects
| | ...
| +-- protection-type? identityref
| +-- restoration-type? identityref
| +-- restoration-scheme? identityref
| +-- te-topology-identifier
| | +-- provider-id? te-global-id
| | +-- client-id? te-global-id
| | +-- topology-id? te-topology-id
| +-- te-bandwidth
| | ...
| +-- link-protection? identityref
| +-- setup-priority? uint8
| +-- hold-priority? uint8
| +-- signaling-type? identityref
| +-- hierarchy
| +-- dependency-tunnels
| | ...
| +-- hierarchical-link
| ...
The path requests that are intended to be used within the same tunnel
should reference the same entry in the tunnel-attributes list. This
allows:
* avoiding repeating the same set of per-tunnel parameters on
multiple requested paths;
* the server to understand what attributes are intended to be
configured on a per-tunnel basis (e.g., the te-bandwidth
configured in the tunnel-attributes) and what attributes are
intended to be configured on a per-path basis(e.g., the te-
bandwidth configured in the path-request). This could be useful
especially when the server also creates a TE tunnel instance
within the operational datastore to report the computed paths, as
described in Section 3.3.1: in this case, the tunnel-name is also
used as the suggested name for that TE tunnel instance.
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The YANG data model allows also including requests for paths
intended to modify existing tunnels (e.g., adding a protection
path for an existing un-protected tunnel). In this case, the per-
tunnel attributes are already provided in an existing TE tunnel
instance and do not need to be re-configured in the path
computation request RPC. Therefore, these requests should
reference an existing TE tunnel instance.
It is also possible to request computing paths without indicating
in which tunnel they are intended to be used (e.g., in case of an
unprotected tunnel). In this case, the per-tunnel attributes
could be provided together with the per-path attributes in the
path request, without using the tunnel-attributes list.
The choices below are defined to distinguish the cases above:
* whether the per-tunnel attributes are configured by reference
(providing a leafref), to:
- either a TE tunnel instance, if it exists;
- or to an entry of the tunnel-attributes list, if the TE tunnel
instance does not exist;
* or by value, providing the set of tunnel attributes within the
path request:
| +-- (tunnel-attributes)?
| | +--:(reference)
| | | +-- tunnel-reference
| | | +-- (tunnel-exist)
| | | | +--:(tunnel-ref)
| | | | | +-- tunnel-ref te:tunnel-ref
| | | | +--:(tunnel-attributes-ref)
| | | | +-- tunnel-attributes-ref leafref
| | | +-- path-name? string
| | | +-- (path-role)
| | | ...
| | +--:(value)
| | +-- tunnel-name? string
| | +-- path-name? string
| | +-- (path-role)?
| | | ...
| | ...
| | +-- encoding? identityref
| | +-- switching-type? identityref
| | ...
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5.3.1. Tunnel attributes specified by value
The (value) case provides the set of attributes that are configured
only on per-tunnel basis (e.g., tunnel-name, source/destination TTP,
encoding and switching-type).
In this case, it is assumed that the requested path will be the only
path within a tunnel.
If the only path within a tunnel is the transit segment of a multi-
domain end-to-end path, it can be of any type (primary, secondary,
reverse-primary or reverse-secondary). The (path-role) choice is
used to specify its role in the path request:
| | +-- (path-role)?
| | | +--:(primary-path)
| | | +--:(secondary-path)
| | | | +-- secondary-path!
| | | | +-- primary-path-name? string
| | | +--:(primary-reverse-path)
| | | | +-- primary-reverse-path!
| | | | +-- primary-path-name? string
| | | +--:(secondary-reverse-path)
| | | +-- secondary-reverse-path!
| | | +-- primary-path-name? string
| | | +-- primary-reverse-path-name? string
In all the other cases, the only path within a tunnel is a primary
path.
The secondary-path, the primary-reverse-path and the secondary-
reverse-path are presence container used to indicate the role of the
path: by default, the path is assumed to be a primary path.
They optionally can contain the name of the primary-path under which
the requested path could be associated within the YANG tree structure
defined in [I-D.ietf-teas-yang-te], which could be useful when the
server also creates a TE tunnel instance within the operational
datastore to report the computed paths, as described in
Section 3.3.1: in this case, the tunnel-name and the path names are
also used as the suggested name for that TE tunnel and path
instances.
5.3.2. Tunnel attributes specified by reference
The (reference) case provides the information needed to associate
multiple path requests that are intended to be used within the same
tunnel.
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In order to indicate the role of the path being requested within the
intended tunnel (e.g., primary or secondary path), the (path-role)
choice is defined:
| | | +-- (path-role)
| | | +--:(primary-path)
| | | | +-- primary-path!
| | | | ...
| | | +--:(secondary-path)
| | | | +-- secondary-path
| | | | ...
| | | +--:(primary-reverse-path)
| | | | +-- primary-reverse-path
| | | | ...
| | | +--:(secondary-reverse-path)
| | | +-- secondary-reverse-path
| | | ...
The primary-path is a presence container used to indicate that the
requested path is intended to be used as a primary path. It can also
contain some attributes which are configured only on primary paths
(e.g., the k-requested-paths).
The secondary-path container indicates that the requested path is
intended to be used as a secondary path and it contains at least
references to one or more primary paths which can use it as a
candidate secondary path:
| | | | +-- secondary-path
| | | | ...
| | | | +-- primary-path-ref* []
| | | | +-- (primary-path-exist)
| | | | +--:(path-ref)
| | | | | +-- primary-path-ref leafref
| | | | +--:(path-request-ref)
| | | | +-- path-request-ref leafref
A requested secondary path can reference any requested primary paths,
and, in case they are intended to be used within an existing TE
tunnel, it could also reference any existing primary-paths.
The secondary-path container can also contain some attributes which
are configured only on secondary paths (e.g., the protection-type).
The primary-reverse-path container indicates that the requested path
is intended to be used as a primary reverse path and it contains only
the reference to the primary path which is intended to use it as a
reverse path:
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| | | | +-- primary-reverse-path
| | | | +-- (primary-path-exist)
| | | | +--:(path-ref)
| | | | | +-- primary-path-ref leafref
| | | | +--:(path-request-ref)
| | | | +-- path-request-ref leafref
A requested primary reverse path can reference either a requested
primary path, or, in case it is intended to be used within an
existing TE tunnel, an existing primary-path.
The secondary-reverse-path container indicates that the requested
path is intended to be used as a secondary reverse path and it
contains at least references to one or more primary paths, whose
primary reverse path can use it as a candidate secondary reverse
path:
| | | +-- secondary-reverse-path
| | | ...
| | | +-- primary-reverse-path* []
| | | +-- (primary-reverse-path-exist)
| | | +--:(path-ref)
| | | | +-- primary-path-ref leafref
| | | +--:(path-request-ref)
| | | +-- path-request-ref leafref
A requested secondary reverse path can reference any requested
primary paths, and, in case they are intended to be used within an
existing TE tunnel, it could reference also existing primary-paths.
The secondary-reverse-path container can also contain some attributes
which are configured only on secondary reverse paths (e.g., the
protection-type).
In case the requested path is a transit segment of a multi-domain
end-to-end path, the primary-path may not be needed to be setup/
computed. However, the request for path computation of a secondary-
path or a primary-reverse or of a secondary-reverse-path requires
that the primary-path exists or it is requested within the same RPC
request. In the latter case, the path request for the primary-path
should have an empty 'route-object-include-exclude' list, as
described in section 5.1.1 of [I-D.ietf-teas-yang-te], to indicate to
the server that path computation is not requested and no path
properties will therefore be returned in the RPC response.
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5.4. Multi-Layer Path Computation
The models supports requesting multi-layer path computation following
the same approach based on dependency tunnels, as defined in
[I-D.ietf-teas-yang-te].
The tunnel-attributes of a given client-layer path request can
reference server-layer TE tunnels which can already exist in the YANG
datastore or be specified in the tunnel-attributes list, within the
same RPC request:
| +-- dependency-tunnels
| | +-- dependency-tunnel* [name]
| | | +-- name -> /te:te/tunnels/tunnel/name
| | | +-- encoding? identityref
| | | +-- switching-type? identityref
| | +-- dependency-tunnel-attributes* [name]
| | +-- name leafref
| | +-- encoding? identityref
| | +-- switching-type? identityref
In a similar way as in [I-D.ietf-teas-yang-te], the server-layer
tunnel attributes should provide the information of what would be the
dynamic link in the client layer topology supported by that tunnel,
if instantiated:
| +-- hierarchical-link
| +-- enable? boolean
| +-- local-te-node-id? te-types:te-node-id
| +-- local-te-link-tp-id? te-types:te-tp-id
| +-- remote-te-node-id? te-types:te-node-id
| +-- te-topology-identifier
| +-- provider-id? te-global-id
| +-- client-id? te-global-id
| +-- topology-id? te-topology-id
It is worth noting that since path computation RPC is stateless, the
dynamic hierarchical links configured for the server-layer tunnel
attributes cannot be used for path computation of any client-layer
path unless explicitly referenced in the dependency-tunnel-attributes
list within the same RPC request.
6. YANG data model for TE path computation
6.1. Tree diagram
Figure 11 below shows the tree diagram of the YANG data model defined
in module ietf-te-path-computation.yang, defined in Section 6.2.
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=============== NOTE: '\' line wrapping per RFC 8792 ================
module: ietf-te-path-computation
augment /te:tunnels-path-compute/te:input/te:path-compute-info:
+-- path-request* [request-id]
| +-- request-id uint32
| +-- compute-priority? uint8
| | {compute-priority}?
| +-- (tunnel-attributes)?
| | +--:(reference)
| | | +-- tunnel-reference
| | | +-- (tunnel-exist)
| | | | +--:(tunnel-ref)
| | | | | +-- tunnel-ref te:tunnel-ref
| | | | +--:(tunnel-attributes-ref)
| | | | +-- tunnel-attributes-ref leafref
| | | +-- path-name? string
| | | +-- (path-role)
| | | +--:(primary-path)
| | | | +-- primary-path!
| | | | +-- preference? uint8
| | | | +-- co-routed? boolean
| | | | +-- k-requested-paths? uint8
| | | +--:(secondary-path)
| | | | +-- secondary-path
| | | | +-- secondary-reverse-path? leafref
| | | | +-- preference? uint8
| | | | +-- protection-type? identityref
| | | | +-- restoration-type? identityref
| | | | +-- restoration-scheme? identityref
| | | | +-- primary-path-ref* []
| | | | +-- (primary-path-exist)
| | | | +--:(path-ref)
| | | | | +-- primary-path-ref leafref
| | | | +--:(path-request-ref)
| | | | +-- path-request-ref leafref
| | | +--:(primary-reverse-path)
| | | | +-- primary-reverse-path
| | | | +-- (primary-path-exist)
| | | | +--:(path-ref)
| | | | | +-- primary-path-ref leafref
| | | | +--:(path-request-ref)
| | | | +-- path-request-ref leafref
| | | +--:(secondary-reverse-path)
| | | +-- secondary-reverse-path
| | | +-- preference? uint8
| | | +-- protection-type? identityref
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| | | +-- restoration-type? identityref
| | | +-- restoration-scheme? identityref
| | | +-- primary-reverse-path* []
| | | +-- (primary-reverse-path-exist)
| | | +--:(path-ref)
| | | | +-- primary-path-ref leafref
| | | +--:(path-request-ref)
| | | +-- path-request-ref leafref
| | +--:(value)
| | +-- tunnel-name? string
| | +-- path-name? string
| | +-- (path-role)?
| | | +--:(primary-path)
| | | +--:(secondary-path)
| | | | +-- secondary-path!
| | | | +-- primary-path-name? string
| | | +--:(primary-reverse-path)
| | | | +-- primary-reverse-path!
| | | | +-- primary-path-name? string
| | | +--:(secondary-reverse-path)
| | | +-- secondary-reverse-path!
| | | +-- primary-path-name? string
| | | +-- primary-reverse-path-name? string
| | +-- k-requested-paths? uint8
| | +-- encoding? identityref
| | +-- switching-type? identityref
| | +-- source
| | | +-- node-id? nw:node-id
| | | +-- te-node-id? te-types:te-node-id
| | | +-- tunnel-tp-id? binary
| | +-- destination
| | | +-- node-id? nw:node-id
| | | +-- te-node-id? te-types:te-node-id
| | | +-- tunnel-tp-id? binary
| | +-- bidirectional? boolean
| | +-- te-topology-identifier
| | +-- provider-id? te-global-id
| | +-- client-id? te-global-id
| | +-- topology-id? te-topology-id
| +-- association-objects
| | +-- association-object* [association-key]
| | | +-- association-key string
| | | +-- type? identityref
| | | +-- id? uint16
| | | +-- source
| | | +-- id? te-gen-node-id
| | | +-- type? enumeration
| | +-- association-object-extended* [association-key]
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| | +-- association-key string
| | +-- type? identityref
| | +-- id? uint16
| | +-- source
| | | +-- id? te-gen-node-id
| | | +-- type? enumeration
| | +-- global-source? uint32
| | +-- extended-id? yang:hex-string
| +-- optimizations
| | +-- (algorithm)?
| | +--:(metric) {path-optimization-metric}?
| | | +-- optimization-metric* [metric-type]
| | | | +-- metric-type identityref
| | | | +-- weight? uint8
| | | | +-- explicit-route-exclude-objects
| | | | | +-- route-object-exclude-object* [index]
| | | | | +-- index uint32
| | | | | +-- (type)?
| | | | | +--:(numbered-node-hop)
| | | | | | +-- numbered-node-hop
| | | | | | +-- node-id-uri? nw:node-id
| | | | | | +-- node-id? te-node-id
| | | | | | +-- hop-type? te-hop-type
| | | | | +--:(numbered-link-hop)
| | | | | | +-- numbered-link-hop
| | | | | | +-- link-tp-id te-tp-id
| | | | | | +-- hop-type? te-hop-type
| | | | | | +-- direction? te-link-direction
| | | | | +--:(unnumbered-link-hop)
| | | | | | +-- unnumbered-link-hop
| | | | | | +-- link-tp-id-uri? nt:tp-id
| | | | | | +-- link-tp-id? te-tp-id
| | | | | | +-- node-id-uri? nw:node-id
| | | | | | +-- node-id? te-node-id
| | | | | | +-- hop-type? te-hop-type
| | | | | | +-- direction?
| | | | | | te-link-direction
| | | | | +--:(as-number)
| | | | | | +-- as-number-hop
| | | | | | +-- as-number inet:as-number
| | | | | | +-- hop-type? te-hop-type
| | | | | +--:(label)
| | | | | | +-- label-hop
| | | | | | +-- te-label
| | | | | | +-- (technology)?
| | | | | | | +--:(generic)
| | | | | | | +-- generic?
| | | | | | | rt-types:generali\
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zed-label
| | | | | | +-- direction?
| | | | | | te-label-direction
| | | | | +--:(srlg)
| | | | | +-- srlg
| | | | | +-- srlg? uint32
| | | | +-- explicit-route-include-objects
| | | | +-- route-object-include-object* [index]
| | | | +-- index uint32
| | | | +-- (type)?
| | | | +--:(numbered-node-hop)
| | | | | +-- numbered-node-hop
| | | | | +-- node-id-uri? nw:node-id
| | | | | +-- node-id? te-node-id
| | | | | +-- hop-type? te-hop-type
| | | | +--:(numbered-link-hop)
| | | | | +-- numbered-link-hop
| | | | | +-- link-tp-id te-tp-id
| | | | | +-- hop-type? te-hop-type
| | | | | +-- direction? te-link-direction
| | | | +--:(unnumbered-link-hop)
| | | | | +-- unnumbered-link-hop
| | | | | +-- link-tp-id-uri? nt:tp-id
| | | | | +-- link-tp-id? te-tp-id
| | | | | +-- node-id-uri? nw:node-id
| | | | | +-- node-id? te-node-id
| | | | | +-- hop-type? te-hop-type
| | | | | +-- direction?
| | | | | te-link-direction
| | | | +--:(as-number)
| | | | | +-- as-number-hop
| | | | | +-- as-number inet:as-number
| | | | | +-- hop-type? te-hop-type
| | | | +--:(label)
| | | | +-- label-hop
| | | | +-- te-label
| | | | +-- (technology)?
| | | | | +--:(generic)
| | | | | +-- generic?
| | | | | rt-types:generali\
zed-label
| | | | +-- direction?
| | | | te-label-direction
| | | +-- tiebreakers
| | | +-- tiebreaker* [tiebreaker-type]
| | | +-- tiebreaker-type identityref
| | +--:(objective-function)
| | {path-optimization-objective-function}?
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| | +-- objective-function
| | +-- objective-function-type? identityref
| +-- named-path-constraint? leafref
| | {te-types:named-path-constraints}?
| +-- te-bandwidth
| | +-- (technology)?
| | +--:(generic)
| | +-- generic? te-bandwidth
| +-- link-protection? identityref
| +-- setup-priority? uint8
| +-- hold-priority? uint8
| +-- signaling-type? identityref
| +-- path-metric-bounds
| | +-- path-metric-bound* [metric-type]
| | +-- metric-type identityref
| | +-- upper-bound? uint64
| +-- path-affinities-values
| | +-- path-affinities-value* [usage]
| | +-- usage identityref
| | +-- value? admin-groups
| +-- path-affinity-names
| | +-- path-affinity-name* [usage]
| | +-- usage identityref
| | +-- affinity-name* [name]
| | +-- name string
| +-- path-srlgs-lists
| | +-- path-srlgs-list* [usage]
| | +-- usage identityref
| | +-- values* srlg
| +-- path-srlgs-names
| | +-- path-srlgs-name* [usage]
| | +-- usage identityref
| | +-- names* string
| +-- disjointness? te-path-disjointness
| +-- explicit-route-objects-always
| | +-- route-object-exclude-always* [index]
| | | +-- index uint32
| | | +-- (type)?
| | | +--:(numbered-node-hop)
| | | | +-- numbered-node-hop
| | | | +-- node-id-uri? nw:node-id
| | | | +-- node-id? te-node-id
| | | | +-- hop-type? te-hop-type
| | | +--:(numbered-link-hop)
| | | | +-- numbered-link-hop
| | | | +-- link-tp-id te-tp-id
| | | | +-- hop-type? te-hop-type
| | | | +-- direction? te-link-direction
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| | | +--:(unnumbered-link-hop)
| | | | +-- unnumbered-link-hop
| | | | +-- link-tp-id-uri? nt:tp-id
| | | | +-- link-tp-id? te-tp-id
| | | | +-- node-id-uri? nw:node-id
| | | | +-- node-id? te-node-id
| | | | +-- hop-type? te-hop-type
| | | | +-- direction? te-link-direction
| | | +--:(as-number)
| | | | +-- as-number-hop
| | | | +-- as-number inet:as-number
| | | | +-- hop-type? te-hop-type
| | | +--:(label)
| | | +-- label-hop
| | | +-- te-label
| | | +-- (technology)?
| | | | +--:(generic)
| | | | +-- generic?
| | | | rt-types:generalized-label
| | | +-- direction? te-label-direction
| | +-- route-object-include-exclude* [index]
| | +-- explicit-route-usage? identityref
| | +-- index uint32
| | +-- (type)?
| | +--:(numbered-node-hop)
| | | +-- numbered-node-hop
| | | +-- node-id-uri? nw:node-id
| | | +-- node-id? te-node-id
| | | +-- hop-type? te-hop-type
| | +--:(numbered-link-hop)
| | | +-- numbered-link-hop
| | | +-- link-tp-id te-tp-id
| | | +-- hop-type? te-hop-type
| | | +-- direction? te-link-direction
| | +--:(unnumbered-link-hop)
| | | +-- unnumbered-link-hop
| | | +-- link-tp-id-uri? nt:tp-id
| | | +-- link-tp-id? te-tp-id
| | | +-- node-id-uri? nw:node-id
| | | +-- node-id? te-node-id
| | | +-- hop-type? te-hop-type
| | | +-- direction? te-link-direction
| | +--:(as-number)
| | | +-- as-number-hop
| | | +-- as-number inet:as-number
| | | +-- hop-type? te-hop-type
| | +--:(label)
| | | +-- label-hop
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| | | +-- te-label
| | | +-- (technology)?
| | | | +--:(generic)
| | | | +-- generic?
| | | | rt-types:generalized-label
| | | +-- direction? te-label-direction
| | +--:(srlg)
| | +-- srlg
| | +-- srlg? uint32
| +-- path-in-segment!
| | +-- label-restrictions
| | +-- label-restriction* [index]
| | +-- restriction? enumeration
| | +-- index uint32
| | +-- label-start
| | | +-- te-label
| | | +-- (technology)?
| | | | +--:(generic)
| | | | +-- generic? rt-types:generalized-label
| | | +-- direction? te-label-direction
| | +-- label-end
| | | +-- te-label
| | | +-- (technology)?
| | | | +--:(generic)
| | | | +-- generic? rt-types:generalized-label
| | | +-- direction? te-label-direction
| | +-- label-step
| | | +-- (technology)?
| | | +--:(generic)
| | | +-- generic? int32
| | +-- range-bitmap? yang:hex-string
| +-- path-out-segment!
| | +-- label-restrictions
| | +-- label-restriction* [index]
| | +-- restriction? enumeration
| | +-- index uint32
| | +-- label-start
| | | +-- te-label
| | | +-- (technology)?
| | | | +--:(generic)
| | | | +-- generic? rt-types:generalized-label
| | | +-- direction? te-label-direction
| | +-- label-end
| | | +-- te-label
| | | +-- (technology)?
| | | | +--:(generic)
| | | | +-- generic? rt-types:generalized-label
| | | +-- direction? te-label-direction
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| | +-- label-step
| | | +-- (technology)?
| | | +--:(generic)
| | | +-- generic? int32
| | +-- range-bitmap? yang:hex-string
| +-- requested-metrics* [metric-type]
| | +-- metric-type identityref
| +-- return-srlgs? boolean
| +-- return-affinities? boolean
| +-- requested-state!
| +-- timer? uint16
| +-- transaction-id? string
+-- tunnel-attributes* [tunnel-name]
| +-- tunnel-name string
| +-- encoding? identityref
| +-- switching-type? identityref
| +-- source
| | +-- node-id? nw:node-id
| | +-- te-node-id? te-types:te-node-id
| | +-- tunnel-tp-id? binary
| +-- destination
| | +-- node-id? nw:node-id
| | +-- te-node-id? te-types:te-node-id
| | +-- tunnel-tp-id? binary
| +-- bidirectional? boolean
| +-- association-objects
| | +-- association-object* [association-key]
| | | +-- association-key string
| | | +-- type? identityref
| | | +-- id? uint16
| | | +-- source
| | | +-- id? te-gen-node-id
| | | +-- type? enumeration
| | +-- association-object-extended* [association-key]
| | +-- association-key string
| | +-- type? identityref
| | +-- id? uint16
| | +-- source
| | | +-- id? te-gen-node-id
| | | +-- type? enumeration
| | +-- global-source? uint32
| | +-- extended-id? yang:hex-string
| +-- protection-type? identityref
| +-- restoration-type? identityref
| +-- restoration-scheme? identityref
| +-- network-id? nw:network-id
| +-- te-topology-identifier
| | +-- provider-id? te-global-id
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| | +-- client-id? te-global-id
| | +-- topology-id? te-topology-id
| +-- te-bandwidth
| | +-- (technology)?
| | +--:(generic)
| | +-- generic? te-bandwidth
| +-- link-protection? identityref
| +-- setup-priority? uint8
| +-- hold-priority? uint8
| +-- signaling-type? identityref
| +-- hierarchy
| +-- dependency-tunnels
| | +-- dependency-tunnel* [name]
| | | +-- name -> /te:te/tunnels/tunnel/name
| | | +-- encoding? identityref
| | | +-- switching-type? identityref
| | +-- dependency-tunnel-attributes* [name]
| | +-- name leafref
| | +-- encoding? identityref
| | +-- switching-type? identityref
| +-- hierarchical-link
| +-- enable? boolean
| +-- local-node-id? nw:node-id
| +-- local-te-node-id? te-types:te-node-id
| +-- local-link-tp-id? nt:tp-id
| +-- local-te-link-tp-id? te-types:te-tp-id
| +-- remote-link-tp-id? nt:tp-id
| +-- remote-te-node-id? te-types:te-node-id
| +-- network-id? nw:network-id
| +-- te-topology-identifier
| +-- provider-id? te-global-id
| +-- client-id? te-global-id
| +-- topology-id? te-topology-id
+-- synchronization* [] {svec}?
+-- svec
| +-- relaxable? boolean
| +-- disjointness? te-path-disjointness
| +-- request-id* uint32
+-- svec-constraints
| +-- path-metric-bound* [metric-type]
| +-- metric-type identityref
| +-- upper-bound? uint64
+-- path-srlgs-lists
| +-- path-srlgs-list* [usage]
| +-- usage identityref
| +-- values* srlg
+-- path-srlgs-names
| +-- path-srlgs-name* [usage]
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| +-- usage identityref
| +-- names* string
+-- exclude-objects
| +-- excludes* []
| +-- (type)?
| +--:(numbered-node-hop)
| | +-- numbered-node-hop
| | +-- node-id-uri? nw:node-id
| | +-- node-id? te-node-id
| | +-- hop-type? te-hop-type
| +--:(numbered-link-hop)
| | +-- numbered-link-hop
| | +-- link-tp-id te-tp-id
| | +-- hop-type? te-hop-type
| | +-- direction? te-link-direction
| +--:(unnumbered-link-hop)
| | +-- unnumbered-link-hop
| | +-- link-tp-id-uri? nt:tp-id
| | +-- link-tp-id? te-tp-id
| | +-- node-id-uri? nw:node-id
| | +-- node-id? te-node-id
| | +-- hop-type? te-hop-type
| | +-- direction? te-link-direction
| +--:(as-number)
| | +-- as-number-hop
| | +-- as-number inet:as-number
| | +-- hop-type? te-hop-type
| +--:(label)
| +-- label-hop
| +-- te-label
| +-- (technology)?
| | +--:(generic)
| | +-- generic?
| | rt-types:generalized-label
| +-- direction? te-label-direction
+-- optimizations
+-- (algorithm)?
+--:(metric) {te-types:path-optimization-metric}?
| +-- optimization-metric* [metric-type]
| +-- metric-type identityref
| +-- weight? uint8
+--:(objective-function)
{te-types:path-optimization-objective-function\
}?
+-- objective-function
+-- objective-function-type? identityref
augment /te:tunnels-path-compute/te:output/te:path-compute-result:
+--ro response* [response-id]
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+--ro response-id uint32
+--ro computed-paths-properties
| +--ro computed-path-properties* [k-index]
| +--ro k-index uint8
| +--ro path-properties
| +--ro path-metric* [metric-type]
| | +--ro metric-type identityref
| | +--ro accumulative-value? uint64
| +--ro path-affinities-values
| | +--ro path-affinities-value* [usage]
| | +--ro usage identityref
| | +--ro value? admin-groups
| +--ro path-affinity-names
| | +--ro path-affinity-name* [usage]
| | +--ro usage identityref
| | +--ro affinity-name* [name]
| | +--ro name string
| +--ro path-srlgs-lists
| | +--ro path-srlgs-list* [usage]
| | +--ro usage identityref
| | +--ro values* srlg
| +--ro path-srlgs-names
| | +--ro path-srlgs-name* [usage]
| | +--ro usage identityref
| | +--ro names* string
| +--ro path-route-objects
| | +--ro path-route-object* [index]
| | +--ro index uint32
| | +--ro (type)?
| | +--:(numbered-node-hop)
| | | +--ro numbered-node-hop
| | | +--ro node-id-uri? nw:node-id
| | | +--ro node-id? te-node-id
| | | +--ro hop-type? te-hop-type
| | +--:(numbered-link-hop)
| | | +--ro numbered-link-hop
| | | +--ro link-tp-id te-tp-id
| | | +--ro hop-type? te-hop-type
| | | +--ro direction? te-link-direction
| | +--:(unnumbered-link-hop)
| | | +--ro unnumbered-link-hop
| | | +--ro link-tp-id-uri? nt:tp-id
| | | +--ro link-tp-id? te-tp-id
| | | +--ro node-id-uri? nw:node-id
| | | +--ro node-id? te-node-id
| | | +--ro hop-type? te-hop-type
| | | +--ro direction?
| | | te-link-direction
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| | +--:(as-number)
| | | +--ro as-number-hop
| | | +--ro as-number inet:as-number
| | | +--ro hop-type? te-hop-type
| | +--:(label)
| | +--ro label-hop
| | +--ro te-label
| | +--ro (technology)?
| | | +--:(generic)
| | | +--ro generic?
| | | rt-types:generalized\
-label
| | +--ro direction?
| | te-label-direction
| +--ro te-bandwidth
| | +--ro (technology)?
| | +--:(generic)
| | +--ro generic? te-bandwidth
| +--ro disjointness-type?
| te-types:te-path-disjointness
+--ro computed-path-error-infos
| +--ro computed-path-error-info* []
| +--ro error-description? string
| +--ro error-timestamp? yang:date-and-time
| +--ro error-reason? identityref
+--ro tunnel-ref? te:tunnel-ref
+--ro (path-role)?
+--:(primary)
| +--ro primary-path-ref? leafref
+--:(primary-reverse)
| +--ro primary-reverse-path-ref? leafref
+--:(secondary)
| +--ro secondary-path-ref? leafref
+--:(secondary-reverse)
+--ro secondary-reverse-path-ref? leafref
augment /te:tunnels-actions/te:input/te:tunnel-info/te:filter-type:
+--:(path-compute-transactions)
+-- path-compute-transaction-id* string
augment /te:tunnels-actions/te:output:
+--ro path-computed-delete-result
+--ro path-compute-transaction-id* string
Figure 11: TE path computation tree diagram
6.2. YANG module
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<CODE BEGINS> file "ietf-te-path-computation@2023-06-27.yang"
module ietf-te-path-computation {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-te-path-computation";
prefix te-pc;
import ietf-te {
prefix te;
reference
"RFCYYYY: A YANG Data Model for Traffic Engineering Tunnels
and Interfaces";
}
/* Note: The RFC Editor will replace YYYY with the number assigned
to the RFC once draft-ietf-teas-yang-te becomes an RFC.*/
import ietf-te-types {
prefix te-types;
reference
"RFCZZZZ: Updated Common YANG Data Types for Traffic
Engineering";
}
/* Note: The RFC Editor will replace ZZZZ with the number assigned
to the RFC once draft-ietf-teas-rfc8776-update becomes an RFC.*/
organization
"Traffic Engineering Architecture and Signaling (TEAS)
Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/teas/>
WG List: <mailto:teas@ietf.org>
Editor: Italo Busi
<mailto:italo.busi@huawei.com>
Editor: Sergio Belotti
<mailto:sergio.belotti@nokia.com>
Editor: Victor Lopez
<mailto:victor.lopez@nokia.com>
Editor: Oscar Gonzalez de Dios
<mailto:oscar.gonzalezdedios@telefonica.com>
Editor: Anurag Sharma
<mailto:ansha@google.com>
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Editor: Yan Shi
<mailto:shiyan49@chinaunicom.cn>
Editor: Ricard Vilalta
<mailto:ricard.vilalta@cttc.es>
Editor: Karthik Sethuraman
<mailto:karthik.sethuraman@necam.com>
Editor: Michael Scharf
<mailto:michael.scharf@gmail.com>
Editor: Daniele Ceccarelli
<mailto:daniele.ceccarelli@ericsson.com>
";
description
"This module defines a YANG data model for requesting Traffic
Engineering (TE) path computation. The YANG data model defined
in this document augments the RPCs defined in the generic TE
module (ietf-te).
The model fully conforms to the
Network Management Datastore Architecture (NMDA).
Copyright (c) 2023 IETF Trust and the persons
identified as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Revised
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";
// RFC Ed.: replace XXXX with actual RFC number and remove
// this note
// replace the revision date with the module publication date
// the format is (year-month-day)
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revision 2023-06-27 {
description
"Initial revision";
reference
"RFC XXXX: A YANG Data Model for requesting path computation";
}
// RFC Ed.: replace XXXX with actual RFC number and remove
// this note
/*
* Features
*/
feature svec {
description
"This feature indicates that the server supports synchronized
path computation requests.";
reference
"Section 7.13 of RFC5440: Path Computation Element (PCE)
Communication Protocol (PCEP).";
}
feature compute-priority {
description
"This feature indicates that the server supports path
computation request's priority";
reference
"Section 7.4.1 of RFC5440: Path Computation Element (PCE)
Communication Protocol (PCEP).";
}
/*
* Identities
*/
identity tunnel-action-path-compute-delete {
base te-types:tunnel-action-type;
description
"Action type to delete the transient states
of computed paths, as described in section 3.3.1 of
RFC XXXX.";
reference
"RFC XXXX: A YANG Data Model for requesting path computation";
}
/*
* Groupings
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*/
grouping protection-restoration-properties {
description
"This grouping defines the restoration and protection types
for a path in the path computation request.";
leaf protection-type {
type identityref {
base te-types:lsp-protection-type;
}
default "te-types:lsp-protection-unprotected";
description
"LSP protection type.";
}
leaf restoration-type {
type identityref {
base te-types:lsp-restoration-type;
}
default "te-types:lsp-restoration-restore-any";
description
"LSP restoration type.";
}
leaf restoration-scheme {
type identityref {
base te-types:restoration-scheme-type;
}
default "te-types:restoration-scheme-preconfigured";
description
"LSP restoration scheme.";
}
} // grouping protection-restoration-properties
grouping requested-info {
description
"This grouping defines the information which is requested
(e.g., metrics), in the path computation request, to be
returned in the path computation response.";
list requested-metrics {
key "metric-type";
description
"The list of the requested metrics.
The metrics listed here MUST be returned in the response.
Returning other metrics in the response is OPTIONAL.";
leaf metric-type {
type identityref {
base te-types:path-metric-type;
}
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description
"The metric requested to be returned in the response";
}
}
leaf return-srlgs {
type boolean;
default "false";
description
"If true, path Shared Risk Link Groups (SRLGs) MUST be
returned in the response.
If false, returning path SRLGs in the response OPTIONAL.";
}
leaf return-affinities {
type boolean;
default "false";
description
"If true, path affinities MUST be returned in the response.
If false, returning path affinities in the response is
OPTIONAL.";
}
} // grouping requested-info
grouping requested-state {
description
"Configuration for the transient state used
to report the computed path";
container requested-state {
presence
"Request temporary reporting of the computed path state";
description
"Configures attributes for the temporary reporting of the
computed path state (e.g., expiration timer).";
leaf timer {
type uint16;
units "minutes";
default "10";
description
"The timeout after which the transient state reporting
the computed path SHOULD be removed.";
}
leaf transaction-id {
type string;
description
"The transaction-id associated with this path computation
to be used for fast deletion of the transient states
associated with multiple path computations.
This transaction-id can be used to explicitly delete all
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the transient states of all the computed paths associated
with the same transaction-id.
When one path associated with a transaction-id is setup,
the transient states of all the other computed paths
with the same transaction-id are automatically removed.
If not specified, the transient state is removed only
when the timer expires (when the timer is specified)
or not created at all (stateless path computation,
when the timer is not specified).";
}
}
} // grouping requested-state
grouping reported-state {
description
"This grouping defines the information, returned in the path
computation response, reporting the transient state related
to the computed path";
leaf tunnel-ref {
type te:tunnel-ref;
description
"
Reference to the tunnel that reports the transient state
of the computed path.
If no transient state is created, this attribute is
omitted.
";
}
choice path-role {
description
"The transient state of the computed path can be reported
as a primary, primary-reverse, secondary or
a secondary-reverse path of a te-tunnel";
case primary {
leaf primary-path-ref {
type leafref {
path "/te:te/te:tunnels/"
+ "te:tunnel[te:name=current()/../tunnel-ref]/"
+ "te:primary-paths/te:primary-path/"
+ "te:name";
}
must '../tunnel-ref' {
description
"The primary-path name can only be reported
if the tunnel name is also reported.";
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}
description
"
Reference to the primary-path that reports
the transient state of the computed path.
If no transient state is created,
this attribute is omitted.
";
}
} // case primary
case primary-reverse {
leaf primary-reverse-path-ref {
type leafref {
path "/te:te/te:tunnels/"
+ "te:tunnel[te:name=current()/../tunnel-ref]/"
+ "te:primary-paths/te:primary-path/"
+ "te:name";
}
must '../tunnel-ref' {
description
"The primary-reverse-path name can only be reported
if the tunnel name is also reported.";
}
description
"
Reference to the primary-reverse-path that reports
the transient state of the computed path.
If no transient state is created,
this attribute is omitted.
";
}
} // case primary-reverse
case secondary {
leaf secondary-path-ref {
type leafref {
path "/te:te/te:tunnels/"
+ "te:tunnel[te:name=current()/../tunnel-ref]/"
+ "te:secondary-paths/te:secondary-path/"
+ "te:name";
}
must '../tunnel-ref' {
description
"The secondary-path name can only be reported
if the tunnel name is also reported.";
}
description
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"
Reference to the secondary-path that reports
the transient state of the computed path.
If no transient state is created,
this attribute is omitted.
";
}
} // case secondary
case secondary-reverse {
leaf secondary-reverse-path-ref {
type leafref {
path "/te:te/te:tunnels/"
+ "te:tunnel[te:name=current()/../tunnel-ref]/"
+ "te:secondary-reverse-paths/"
+ "te:secondary-reverse-path/te:name";
}
must '../tunnel-ref' {
description
"The secondary-reverse-path name can only be reported
if the tunnel name is also reported.";
}
description
"
Reference to the secondary-reverse-path that reports
the transient state of the computed path.
If no transient state is created,
this attribute is omitted.
";
}
} // case secondary
} // choice path
} // grouping reported-state
grouping synchronization-constraints {
description
"Global constraints applicable to synchronized path
computation requests.";
container svec-constraints {
description
"global svec constraints";
list path-metric-bound {
key "metric-type";
description
"list of bound metrics";
leaf metric-type {
type identityref {
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base te-types:svec-metric-type;
}
description
"SVEC metric type.";
reference
"RFC5541: Encoding of Objective Functions in the Path
Computation Element Communication Protocol (PCEP).";
}
leaf upper-bound {
type uint64;
description
"Upper bound on SVEC metric";
}
}
}
uses te-types:generic-path-srlgs;
container exclude-objects {
description
"Resources to be excluded";
list excludes {
description
"List of Explicit Route Objects to always exclude
from synchronized path computation";
uses te-types:explicit-route-hop;
}
}
} // grouping synchronization-constraints
grouping synchronization-optimization {
description
"Optimizations applicable to synchronized path
computation requests.";
container optimizations {
description
"The objective function container that includes attributes
to impose when computing a synchronized set of paths";
choice algorithm {
description
"Optimizations algorithm.";
case metric {
if-feature "te-types:path-optimization-metric";
list optimization-metric {
key "metric-type";
description
"svec path metric type";
leaf metric-type {
type identityref {
base te-types:svec-metric-type;
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}
description
"TE path metric type usable for computing a set of
synchronized requests";
}
leaf weight {
type uint8;
description
"Metric normalization weight";
}
}
}
case objective-function {
if-feature
"te-types:path-optimization-objective-function";
container objective-function {
description
"The objective function container that includes
attributes to impose when computing a TE path";
leaf objective-function-type {
type identityref {
base te-types:svec-objective-function-type;
}
description
"Objective function entry";
}
}
}
}
}
} // grouping synchronization-optimization
grouping synchronization-info {
description
"Information for synchronized path computation requests.";
list synchronization {
description
"List of Synchronization VECtors.";
container svec {
description
"Synchronization VECtor";
leaf relaxable {
type boolean;
default "true";
description
"If this leaf is true, taking into account this svec is
OPTIONAL and the path computation process is
free to ignore svec content.
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Otherwise, it MUST take into account this svec.";
}
uses te-types:generic-path-disjointness;
leaf-list request-id {
type uint32;
description
"This list reports the set of path computation
requests that are requested to be synchronized.";
}
}
uses synchronization-constraints;
uses synchronization-optimization;
}
} // grouping synchronization-info
/*
* Augment TE RPCs
*/
augment "/te:tunnels-path-compute/te:input/te:path-compute-info" {
description
"Augments Path Computation RPC input";
list path-request {
key "request-id";
description
"The list of the requested paths to be computed";
leaf request-id {
type uint32;
mandatory true;
description
"Each path computation request is uniquely identified
within the RPC request by the request-id.";
}
leaf compute-priority {
if-feature compute-priority;
type uint8;
default 0;
description
"The path computation request's priority (from 1 to 7)
which can be used to constraint the order by which the
path computation server processes the path computation
requests.
A higher numerical value of the priority field reflects a
higher priority.
It MUST be set to the default value (i.e., 0) when
unused.";
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reference
"Section 7.4.1 of RFC5440: Path Computation Element (PCE)
Communication Protocol (PCEP).";
}
choice tunnel-attributes {
default "value";
description
"Whether the tunnel attributes are specified by value
within this path computation request or by reference.
The reference could be either to an existing te-tunnel
or to an entry in the tunnel-attributes list";
case reference {
container tunnel-reference {
description
"Attributes for a requested path that belongs to
either an exiting te-tunnel or to an entry in the
tunnel-attributes list.";
choice tunnel-exist {
mandatory true;
description
"Whether the tunnel reference is to an existing
te-tunnel or to an entry in the tunnel-attributes
list";
case tunnel-ref {
leaf tunnel-ref {
type te:tunnel-ref;
mandatory true;
description
"The referenced te-tunnel instance";
}
} // case tunnel-ref
case tunnel-attributes-ref {
leaf tunnel-attributes-ref {
type leafref {
path "/te:tunnels-path-compute/"
+ "te:path-compute-info/"
+ "te-pc:tunnel-attributes/te-pc:tunnel-name";
}
mandatory true;
description
"The referenced te-tunnel instance";
}
} // case tunnel-attributes-ref
} // choice tunnel-exist
leaf path-name {
type string;
description
"TE path name.";
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}
choice path-role {
mandatory true;
description
"Whether this path is a primary, or a reverse
primary, or a secondary, or a reverse secondary
path.";
case primary-path {
container primary-path {
presence "Indicates that the requested path
is a primary path";
description
"TE primary path";
uses te:path-forward-properties;
uses te:k-requested-paths;
} // container primary-path
} // case primary-path
case secondary-path {
container secondary-path {
description
"TE secondary path";
leaf secondary-reverse-path {
type leafref {
path "/te:tunnels-path-compute/"
+ "te:path-compute-info/te-pc:path-request/"
+ "te-pc:request-id";
}
description
"A reference to the reverse secondary path
when co-routed with the secondary path.";
}
leaf preference {
type uint8 {
range "1..255";
}
default "1";
description
"Specifies a preference for this path. The
lower the number higher the preference.";
}
uses protection-restoration-properties;
list primary-path-ref {
min-elements 1;
description
"The list of primary paths that reference
this path as a candidate secondary path";
choice primary-path-exist {
mandatory true;
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description
"Whether the path reference is to an existing
te-tunnel path or to another path request";
case path-ref {
leaf primary-path-ref {
type leafref {
path "/te:te/te:tunnels/te:tunnel"
+ "[te:name=current()/../../../"
+ "tunnel-ref]/te:primary-paths/"
+ "te:primary-path/te:name";
}
must '../../../tunnel-ref' {
description
"The primary-path can be referenced
if also the tunnel is referenced.";
}
mandatory true;
description
"The referenced primary path";
}
} // case path-ref
case path-request-ref {
leaf path-request-ref {
type leafref {
path "/te:tunnels-path-compute/"
+ "te:path-compute-info/"
+ "te-pc:path-request/"
+ "te-pc:request-id";
}
mandatory true;
description
"The referenced primary path request";
}
} // case path-request-ref
} // choice primary-path-exist
} // list primary-path-ref
} // container secondary-path
} // case secondary-path
case primary-reverse-path {
container primary-reverse-path {
description
"TE primary reverse path";
choice primary-path-exist {
mandatory true;
description
"Whether the path reference to the primary
paths for which this path is the reverse-path
is to an existing te-tunnel path or to
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another path request.";
case path-ref {
leaf primary-path-ref {
type leafref {
path "/te:te/te:tunnels/te:tunnel[te:name"
+ "=current()/../../tunnel-ref]/"
+ "te:primary-paths/te:primary-path/"
+ "te:name";
}
must '../../tunnel-ref' {
description
"The primary-path can be referenced
if also the tunnel is referenced.";
}
mandatory true;
description
"The referenced primary path";
}
} // case path-ref
case path-request-ref {
leaf path-request-ref {
type leafref {
path "/te:tunnels-path-compute/"
+ "te:path-compute-info/"
+ "te-pc:path-request/"
+ "te-pc:request-id";
}
mandatory true;
description
"The referenced primary path request";
}
} // case path-request-ref
} // choice primary-path-exist
} // container primary-reverse-path
} // case primary-reverse-path
case secondary-reverse-path {
container secondary-reverse-path {
description
"TE secondary reverse path";
// uses te:path-preference;
leaf preference {
type uint8 {
range "1..255";
}
default "1";
description
"Specifies a preference for this path. The
lower the number higher the preference.";
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}
uses protection-restoration-properties;
list primary-reverse-path {
min-elements 1;
description
"The list of primary reverse paths that
reference this path as a candidate
secondary reverse path";
choice primary-reverse-path-exist {
mandatory true;
description
"Whether the path reference is to an existing
te-tunnel path or to another path request";
case path-ref {
leaf primary-path-ref {
type leafref {
path "/te:te/te:tunnels/te:tunnel"
+ "[te:name=current()/../../../"
+ "tunnel-ref]/te:primary-paths/"
+ "te:primary-path/te:name";
}
must '../../../tunnel-ref' {
description
"The primary-path can be referenced
if also the tunnel is referenced.";
}
mandatory true;
description
"The referenced primary path";
}
} // case path-ref
case path-request-ref {
leaf path-request-ref {
type leafref {
path "/te:tunnels-path-compute/"
+ "te:path-compute-info/"
+ "te-pc:path-request/"
+ "te-pc:request-id";
}
mandatory true;
description
"The referenced primary reverse path
request";
}
} // case path-request-ref
} // choice primary-reverse-path-exist
} // list primary-reverse-path-ref
} // container secondary-reverse-path
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} // case secondary-reverse-path
} // choice tunnel-path-role
}
} // case reference
case value {
leaf tunnel-name {
type string;
description
"TE tunnel name.";
}
leaf path-name {
type string;
description
"TE path name.";
}
choice path-role {
when 'not (./source) and not (./destination)' {
description
"When the tunnel attributes are specified by value
within this path computation, it is assumed that the
requested path will be the only path of a tunnel.
If the requested path is a transit segment path
(i.e., the source and destination containers are
not present), it could be of any type. Otherwise it
could only be a primary path.";
}
default primary-path;
description
"Indicates whether the requested path is a primary
path, a secondary path, a reverse primary path or a
reverse secondary path.";
case primary-path {
description
"The requested path is a primary path.";
}
container secondary-path {
presence
"Indicates that the requested path is a secondary
path.";
description
"The name of the primary path which the requested
secondary path belongs to.";
leaf primary-path-name {
type string;
description
"TE primary path name.";
}
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} // container secondary-path
container primary-reverse-path {
presence
"Indicates that the requested path is a primary
reverse path.";
description
"The name of the primary path which the requested
primary reverse path belongs to.";
leaf primary-path-name {
type string;
description
"TE primary path name.";
}
} // container primary-reverse-path
container secondary-reverse-path {
presence
"Indicates that the requested path is a secondary
reverse path.";
description
"The names of the primary path and of the primary
reverse path which the requested secondary reverse
path belongs to.";
leaf primary-path-name {
type string;
description
"TE primary path name.";
}
leaf primary-reverse-path-name {
type string;
description
"TE primary reverse path name.";
}
} // container primary-reverse-path
} // choice path-role
uses te:k-requested-paths;
uses te-types:encoding-and-switching-type;
uses te:tunnel-common-attributes;
uses te-types:te-topology-identifier;
} // case value
} // choice tunnel-attributes
uses te:path-compute-info;
uses requested-info;
uses requested-state;
}
list tunnel-attributes {
key "tunnel-name";
description
"Tunnel attributes common to multiple request paths";
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leaf tunnel-name {
type string;
description
"TE tunnel name.";
}
uses te-types:encoding-and-switching-type;
uses te:tunnel-common-attributes;
uses te:tunnel-associations-properties;
uses protection-restoration-properties;
uses te-types:tunnel-constraints;
uses te:tunnel-hierarchy-properties {
augment "hierarchy/dependency-tunnels" {
description
"Augment with the list of dependency tunnel requests.";
list dependency-tunnel-attributes {
key "name";
description
"A tunnel request entry that this tunnel request can
potentially depend on.";
leaf name {
type leafref {
path "/te:tunnels-path-compute/"
+ "te:path-compute-info/te-pc:tunnel-attributes/"
+ "te-pc:tunnel-name";
}
description
"Dependency tunnel request name.";
}
uses te-types:encoding-and-switching-type;
}
}
}
}
uses synchronization-info {
if-feature svec;
}
} // path-compute rpc input
augment "/te:tunnels-path-compute/te:output/"
+ "te:path-compute-result" {
description
"Auguments Path Computation RPC output";
list response {
key "response-id";
config false;
description
"response";
leaf response-id {
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type uint32;
description
"The response-id has the same value of the
corresponding request-id.";
}
uses te:path-computation-response;
uses reported-state;
}
} // path-compute rpc output
augment "/te:tunnels-actions/te:input/te:tunnel-info/"
+ "te:filter-type" {
description
"Augment Tunnels Action RPC input filter types";
case path-compute-transactions {
when "derived-from-or-self(../te:action-info/te:action, "
+ "'tunnel-action-path-compute-delete')";
description
"Path Delete RPC input";
leaf-list path-compute-transaction-id {
type string;
description
"The list of the transaction-id values of the
transient states to be deleted";
}
}
} // path-delete rpc input
augment "/te:tunnels-actions/te:output" {
description
"Augment Tunnels Action RPC output with path delete result";
container path-computed-delete-result {
description
"Path Delete RPC output";
leaf-list path-compute-transaction-id {
type string;
description
"The list of the transaction-id values of the
transient states that have been successfully deleted";
}
}
} // path-delete rpc output
}
<CODE ENDS>
Figure 12: TE path computation YANG module
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7. Security Considerations
This document describes use cases of requesting Path Computation
using YANG data models, which could be used at the ABNO Control
Interface [RFC7491] and/or between controllers in ACTN [RFC8453]. As
such, it does not introduce any new security considerations compared
to the ones related to YANG specification, ABNO specification and
ACTN Framework defined in [RFC7950], [RFC7491] and [RFC8453].
The YANG module defined in this document is designed to be accessed
via the NETCONF protocol [RFC6241] or RESTCONF protocol [RFC8040].
The lowest NETCONF layer is the secure transport layer, and the
mandatory-to-implement secure transport is Secure Shell (SSH)
[RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-
implement secure transport is TLS [RFC8446].
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
The YANG module defined in this document augments the "tunnels-path-
compute" and the "tunnel-actions" RPCs defined in
[I-D.ietf-teas-yang-te]. The security considerations provided in
[I-D.ietf-teas-yang-te] are also applicable to the YANG module
defined in this document.
The RPC defined in this document can also be used for Denial-of-
service (DoS) attacks. The security considerations defines in
section 10.7.2 of [RFC5440] also applies to the use of this RPC.
The definition of the input shaping/policing mechanisms and of their
configuration is outside the scope of this document.
Some of the RPC operations defined in this YANG module may be
considered sensitive or vulnerable in some network environments. It
is thus important to control access to these operations. These are
the operations and their sensitivity/vulnerability:
"te-pc:response/computed-paths-properties": provides the same
information provided by the "te:computed-paths-properties" defined in
[I-D.ietf-teas-yang-te]. The security considerations provided in
[I-D.ietf-teas-yang-te] for the TE tunnel state apply also to this
subtree.
"te-pc:response/te-pc:tunnel-ref", "te-pc:response/te-pc:primary-
path-ref", "te-pc:response/te-pc:primary-reverse-path-ref", "te-
pc:response/te-pc:secondary-path-ref" and "te-pc:response/te-
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pc:secondary-reverse-path-ref" provides a reference where the same
information provided in "te-pc:response/computed-paths-properties" is
temporarly stored with the operational datastore (see Section 3.3.1).
Therefore access to this information does not provide any additional
security issue that the information provided with "te-pc:response/
computed-paths-properties".
"/te:tunnels-actions": the YANG model defined in this document
augments this action with a new action type that allows deleting the
transient states of computed paths (see Section 3.3.1). A malicious
use of this action would have no impact on the paths carrying live
traffic but it would preclude the client from using the "transient
states" to request the set-up of exactly that path, if still
available.
The security considerations spelled out in the YANG specification
[RFC7950] apply for this document as well.
8. IANA Considerations
This document registers the following URIs in the "ns" subregistry
within the "IETF XML registry" [RFC3688].
URI: urn:ietf:params:xml:ns:yang:ietf-te-path-computation
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
This document registers a YANG module in the "YANG Module Names"
registry [RFC7950].
name: ietf-te-path-computation
namespace: urn:ietf:params:xml:ns:yang:ietf-te-path-computation
prefix: te-pc
reference: this document
9. References
9.1. Normative References
[I-D.ietf-teas-rfc8776-update]
Busi, I., Guo, A., Liu, X., Saad, T., and I. Bryskin,
"Common YANG Data Types for Traffic Engineering", Work in
Progress, Internet-Draft, draft-ietf-teas-rfc8776-update-
09, 29 January 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
rfc8776-update-09>.
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[I-D.ietf-teas-yang-te]
Saad, T., Gandhi, R., Liu, X., Beeram, V. P., and I.
Bryskin, "A YANG Data Model for Traffic Engineering
Tunnels, Label Switched Paths and Interfaces", Work in
Progress, Internet-Draft, draft-ietf-teas-yang-te-36, 2
February 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-teas-yang-te-36>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
"A Backward-Recursive PCE-Based Computation (BRPC)
Procedure to Compute Shortest Constrained Inter-Domain
Traffic Engineering Label Switched Paths", RFC 5441,
DOI 10.17487/RFC5441, April 2009,
<https://www.rfc-editor.org/info/rfc5441>.
[RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541,
DOI 10.17487/RFC5541, June 2009,
<https://www.rfc-editor.org/info/rfc5541>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
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[RFC7926] Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
Ceccarelli, D., and X. Zhang, "Problem Statement and
Architecture for Information Exchange between
Interconnected Traffic-Engineered Networks", BCP 206,
RFC 7926, DOI 10.17487/RFC7926, July 2016,
<https://www.rfc-editor.org/info/rfc7926>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8795] Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
O. Gonzalez de Dios, "YANG Data Model for Traffic
Engineering (TE) Topologies", RFC 8795,
DOI 10.17487/RFC8795, August 2020,
<https://www.rfc-editor.org/info/rfc8795>.
9.2. Informative References
[I-D.ietf-ccamp-otn-topo-yang]
Zheng, H., Busi, I., Liu, X., Belotti, S., and O. G. de
Dios, "A YANG Data Model for Optical Transport Network
Topology", Work in Progress, Internet-Draft, draft-ietf-
ccamp-otn-topo-yang-17, 10 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-ccamp-
otn-topo-yang-17>.
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[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
DOI 10.17487/RFC6805, November 2012,
<https://www.rfc-editor.org/info/rfc6805>.
[RFC7446] Lee, Y., Ed., Bernstein, G., Ed., Li, D., and W. Imajuku,
"Routing and Wavelength Assignment Information Model for
Wavelength Switched Optical Networks", RFC 7446,
DOI 10.17487/RFC7446, February 2015,
<https://www.rfc-editor.org/info/rfc7446>.
[RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for
Application-Based Network Operations", RFC 7491,
DOI 10.17487/RFC7491, March 2015,
<https://www.rfc-editor.org/info/rfc7491>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018,
<https://www.rfc-editor.org/info/rfc8453>.
[RFC8454] Lee, Y., Belotti, S., Dhody, D., Ceccarelli, D., and B.
Yoon, "Information Model for Abstraction and Control of TE
Networks (ACTN)", RFC 8454, DOI 10.17487/RFC8454,
September 2018, <https://www.rfc-editor.org/info/rfc8454>.
Appendix A. Examples
This section contains examples of use of the model with RESTCONF
[RFC8040] and JSON encoding.
These examples show how path computation can be requested for the
tunnels configuration provided in Appendix A of
[I-D.ietf-teas-yang-te].
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A.1. Basic Path Computation
This example uses the path computation RPC defined in this document
to request the computation of the path for the tunnel defined in
section 12.1 of of [I-D.ietf-teas-yang-te].
In this case, the TE Tunnel has only one primary path with no
specific constraints.
POST /restconf/operations/ietf-te:tunnels-path-compute HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
{
"ietf-te:input": {
"path-compute-info": {
"ietf-te-path-computation:path-request": [
{
"request-id": 1,
"tunnel-name": "Example_LSP_Tunnel_A_2",
"encoding": "te-types:lsp-encoding-packet",
"source": "192.0.2.1",
"destination": "192.0.2.4",
"bidirectional": "false",
"signaling-type": "te-types:path-setup-rsvp"
}
]
}
}
}
A.2. Path Computation with transient state
This example uses the path computation RPC defined in this document
to request the computation of the path for the tunnel defined in
section 12.1 of of [I-D.ietf-teas-yang-te] requesting some transient
state to be reported within the operational datastore, as described
Section 3.3.1.
In this case, the TE Tunnel has only one primary path with no
specific constraints.
POST /restconf/operations/ietf-te:tunnels-path-compute HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
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{
"ietf-te:input": {
"path-compute-info": {
"ietf-te-path-computation:path-request": [
{
"request-id": 2,
"tunnel-name": "Example_LSP_Tunnel_A_2",
"encoding": "te-types:lsp-encoding-packet",
"source": "192.0.2.1",
"destination": "192.0.2.4",
"bidirectional": "false",
"signaling-type": "te-types:path-setup-rsvp",
"requested-state": {
"transaction-id": "example"
}
}
]
}
}
}
A.3. Path Computation with Global Path Constraint
This example uses the path computation RPC defined in this document
to request the computation of the path for the tunnel defined in
section 12.3 of of [I-D.ietf-teas-yang-te]. The 'named path
constraint' is created in section 12.2 of [I-D.ietf-teas-yang-te]
applies to this path computation request.
POST /restconf/operations/ietf-te:tunnels-path-compute HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
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{
"ietf-te:input": {
"path-compute-info": {
"ietf-te-path-computation:path-request": [
{
"request-id": 3,
"tunnel-name": "Example_LSP_Tunnel_A_4_1",
"path-name": "Simple_LSP_1",
"encoding": "te-types:lsp-encoding-packet",
"source": "192.0.2.1",
"destination": "192.0.2.4",
"bidirectional": "false",
"signaling-type": "path-setup-rsvp",
"named-path-constraint": "max-hop-3",
"requested-state": {}
}
]
}
}
}
A.4. Path Computation with Per-tunnel Path Constraint
This example uses the path computation RPC defined in this document
to request the computation of the path for the tunnel defined in
section 12.4 of of [I-D.ietf-teas-yang-te], using a per tunnel path
constraint.
POST /restconf/operations/ietf-te:tunnels-path-compute HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
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{
"ietf-te:input": {
"path-compute-info": {
"ietf-te-path-computation:path-request": [
{
"request-id": 4,
"tunnel-name": "Example_LSP_Tunnel_A_4_2",
"path-name": "path1",
"encoding": "te-types:lsp-encoding-packet",
"source": "192.0.2.1",
"destination": "192.0.2.4",
"bidirectional": "false",
"signaling-type": "te-types:path-setup-rsvp",
"path-metric-bounds": {
"path-metric-bound": [
{
"metric-type": "te-types:path-metric-hop",
"upper-bound": "3"
}
]
}
}
]
}
}
}
A.5. Path Computation result
This example reports the output of the path computation RPC request
described in Appendix A.4.
HTTP/1.1 200 OK
Host: example.com
Content-Type: application/yang-data+json
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{
"ietf-te:output": {
"path-compute-result": {
"ietf-te-path-computation:response": [
{
"response-id": 3,
"computed-paths-properties": {
"computed-path-properties": [
{
"k-index": "1",
"path-properties": {
"path-route-objects": {
"path-route-object": [
{
"index": "1",
"numbered-node-hop": {
"node-id": "192.0.2.2"
}
},
{
"index": "2",
"numbered-node-hop": {
"node-id": "192.0.2.4"
}
}
]
}
}
}
]
},
"tunnel-ref": "Example_LSP_Tunnel_A_4_1",
"primary-path-ref": "path1"
}
]
}
}
}
A.6. Path Computation with Primary and Secondary Paths
This section contains examples of use of the model to compute primary
and secondary paths described in section 12.6 of
[I-D.ietf-teas-yang-te].
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These examples consider the cases where: - primary and reverse paths
are unidirectional and not co-routed (example-1); - primary and
reverse paths are bidirectional (example-3); - primary and reverse
paths are unidirectional and co-routed (example-4).
POST /restconf/operations/ietf-te:tunnels-path-compute HTTP/1.1
Host: example.com
Content-Type: application/yang-data+json
{
"ietf-te:input": {
"path-compute-info": {
"ietf-te-path-computation:path-request": [
{
"request-id": 1,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "primary-1 (fwd)",
"primary-path": {}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.2",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 2,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "primary-2 (rev)",
"primary-reverse-path": {
"primary-path-request-ref": 1
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.3",
"hop-type": "loose"
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}
}
]
}
},
{
"request-id": 3,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "secondary-1 (fwd)",
"secondary-path": {
"primary-path": [
{
"path-request-ref": 1
}
]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.1"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.2",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 4,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "secondary-2 (fwd)",
"secondary-path": {
"primary-path": [
{
"path-request-ref": 1
}
]
}
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},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.2"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.5",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 5,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "secondary-3 (rev)",
"secondary-reverse-path": {
"primary-reverse-path": [
{
"path-request-ref": 2
}
]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.5"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.4",
"hop-type": "loose"
}
}
]
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}
},
{
"request-id": 6,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "secondary-4 (rev)",
"secondary-reverse-path": {
"primary-reverse-path": [
{
"path-request-ref": 2
}
]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.4"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.3",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 7,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "secondary-5 (rev)",
"secondary-reverse-path": {
"primary-reverse-path": [
{
"path-request-ref": 2
}
]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
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{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.3"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.1",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 8,
"tunnel-reference": {
"tunnel-attributes-ref": "example-3",
"path-name": "primary-1 (bidir)",
"primary-path": {}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.2",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 9,
"tunnel-reference": {
"tunnel-attributes-ref": "example-3",
"path-name": "secondary-1 (bidir)",
"secondary-path": {
"primary-path": [
{
"path-request-ref": 8
}
]
}
},
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"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.1"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.2",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 10,
"tunnel-reference": {
"tunnel-attributes-ref": "example-3",
"path-name": "secondary-2 (bidir)",
"secondary-path": {
"primary-path": [
{
"path-request-ref": 8
}
]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.2"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.5",
"hop-type": "loose"
}
}
]
}
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},
{
"request-id": 11,
"tunnel-reference": {
"tunnel-attributes-ref": "example-4",
"path-name": "primary-1 (fwd)",
"primary-path": {
"co-routed": [null]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.2",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 12,
"tunnel-reference": {
"tunnel-attributes-ref": "example-4",
"path-name": "primary-2 (rev)",
"primary-reverse-path": {
"primary-path-request-ref": 11
}
}
},
{
"request-id": 13,
"tunnel-reference": {
"tunnel-attributes-ref": "example-4",
"path-name": "secondary-1 (fwd)",
"secondary-path": {
"primary-path": [
{
"co-routed": [null],
"path-request-ref": 11
}
]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
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{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.1"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.2",
"hop-type": "loose"
}
}
]
}
},
{
"request-id": 14,
"tunnel-reference": {
"tunnel-attributes-ref": "example-4",
"path-name": "secondary-2 (fwd)",
"secondary-path": {
"primary-path": [
{
"co-routed": [null],
"path-request-ref": 11
}
]
}
},
"explicit-route-objects-always": {
"route-object-include-exclude": [
{
"index": 1,
"numbered-node-hop": {
"node-id": "192.0.2.2"
}
},
{
"index": 2,
"numbered-node-hop": {
"node-id": "192.0.2.5",
"hop-type": "loose"
}
}
]
}
},
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{
"request-id": 15,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "secondary-3 (rev)",
"secondary-reverse-path": {
"primary-reverse-path": [
{
"path-request-ref": 12
}
]
}
}
},
{
"request-id": 16,
"tunnel-reference": {
"tunnel-attributes-ref": "example-1",
"path-name": "secondary-4 (rev)",
"secondary-reverse-path": {
"primary-reverse-path": [
{
"path-request-ref": 12
}
]
}
}
}
],
"ietf-te-path-computation:tunnel-attributes": [
{
"tunnel-name": "example-1",
"source": "192.0.2.1",
"destination": "192.0.2.5",
"bidirectional": "false"
},
{
"tunnel-name": "example-3",
"source": "192.0.2.1",
"destination": "192.0.2.5",
"bidirectional": "true"
},
{
"tunnel-name": "example-4",
"source": "192.0.2.1",
"destination": "192.0.2.5",
"bidirectional": "false"
}
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]
}
}
}
Acknowledgments
The authors would like to thank Karthik Sethuraman, Igor Bryskin and
Xian Zhang for participating in the initial discussions that have
triggered this work and providing valuable insights.
The authors would like to thank the authors of the TE tunnel YANG
data model [I-D.ietf-teas-yang-te], in particular Igor Bryskin,
Vishnu Pavan Beeram, Tarek Saad and Xufeng Liu, for their inputs to
the discussions and support in having consistency between the Path
Computation and TE tunnel YANG data models.
The authors would like to thank Adrian Farrel, Dhruv Dhody, Igor
Bryskin, Julien Meuric and Lou Berger for their valuable input to the
discussions that has clarified that the path being set up is not
necessarily the same as the path that has been previously computed
and, in particular to Dhruv Dhody, for his suggestion to describe the
need for a path verification phase to check that the actual path
being set up meets the required end-to-end metrics and constraints.
The authors would like to thank Aihua Guo, Lou Berger, Shaolong Gan,
Martin Bjorklund and Tom Petch for their useful comments on how to
define XPath statements in YANG RPCs.
The authors would like to thank Haomian Zheng, Yanlei Zheng, Tom
Petch, Aihua Guo and Martin Bjorklund for their review and valuable
comments to this document.
Previous versions of document were prepared using 2-Word-
v2.0.template.dot.
This document was prepared using kramdown.
Contributors
Daniele Ceccarelli
Cisco
Email: daniele.ietf@gmail.com
Victor Lopez
Nokia
Email: victor.lopez@nokia.com
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Ricard Vilalta
CTTC
Email: ricard.vilalta@cttc.es
Michael Scharf
Nokia
Email: michael.scharf@gmail.com
Dieter Beller
Nokia
Email: dieter.beller@nokia.com
Gianmarco Bruno
Ericsson
Email: gianmarco.bruno@ericsson.com
Francesco Lazzeri
Retired
Young Lee
Samsung Electronics
Email: younglee.tx@gmail.com
Carlo Perocchio
Ericsson
Email: carlo.perocchio@ericsson.com
Olivier Dugeon
Orange Labs
Email: olivier.dugeon@orange.com
Julien Meuric
Orange Labs
Email: julien.meuric@orange.com
Authors' Addresses
Italo Busi (editor)
Huawei Technologies
Busi, et al. Expires 17 August 2024 [Page 94]
Internet-Draft Yang for Path Computation February 2024
Email: italo.busi@huawei.com
Sergio Belotti (editor)
Nokia
Email: sergio.belotti@nokia.com
Oscar Gonzalez de Dios
Telefonica
Email: oscar.gonzalezdedios@telefonica.com
Anurag Sharma
Google
Email: ansha@google.com
Yan Shi
China Unicom
Email: shiyan49@chinaunicom.cn
Busi, et al. Expires 17 August 2024 [Page 95]
